feat: new drafts feature and sound spam fix (#174)

## Summary

- **Saved Drafts feature**: Users can now save input content as drafts for later use, and manage them from a new panel
- **Sound spam fix**: The "Working on it!" sound no longer plays repeatedly when Claude makes multiple tool calls in a row

## Details

### Drafts feature
- Rust backend (`drafts.rs`) with `list_drafts`, `save_draft`, `delete_draft`, and `delete_all_drafts` commands, persisted to `hikari-drafts.json` via the Tauri Store plugin
- `draftsStore` wrapping all four commands with timestamp formatting
- `DraftPanel` overlay with insert, per-item two-step delete confirmation, delete-all with confirmation, empty state, and slide-in animation
- **Drafts** button in the top control row (pencil icon)
- **Save as Draft** floppy-disk icon button in the button wrapper (disabled when input is empty)

### Sound spam fix
- Root cause: `resetSoundState` was called on **every** `thinking` state transition, including mid-task transitions (`coding → thinking → coding`)
- Fix: only reset sound state when entering `thinking` from a clean-slate state (`idle`, `success`, or `error`) — states that genuinely mark the end of one task and the start of a new one

## Test plan
- [ ] Save a draft and verify it persists across app restarts
- [ ] Insert a draft and verify it populates the input
- [ ] Delete individual drafts and verify delete-all works
- [ ] Verify "Working on it!" plays once per user message regardless of how many tools are called

✨ This PR was created with help from Hikari~ 🌸

Reviewed-on: #174
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src/lib/stores/drafts.test.ts

@@ -0,0 +1,203 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { get } from "svelte/store";
+import { invoke } from "@tauri-apps/api/core";
+import { setMockInvokeResult } from "../../../vitest.setup";
+import { draftsStore, type Draft } from "./drafts";
+
+const makeDraft = (id: string, content: string, saved_at: string): Draft => ({
+  id,
+  content,
+  saved_at,
+});
+
+describe("Draft interface", () => {
+  it("defines all required fields", () => {
+    const draft: Draft = {
+      id: "draft-123",
+      content: "Hello world",
+      saved_at: "2026-01-01T00:00:00+00:00",
+    };
+
+    expect(draft.id).toBe("draft-123");
+    expect(draft.content).toBe("Hello world");
+    expect(draft.saved_at).toBe("2026-01-01T00:00:00+00:00");
+  });
+
+  it("supports multiline content", () => {
+    const draft: Draft = {
+      id: "multi",
+      content: "Line 1\nLine 2\nLine 3",
+      saved_at: "2026-01-01T00:00:00+00:00",
+    };
+
+    expect(draft.content.includes("\n")).toBe(true);
+    expect(draft.content.split("\n")).toHaveLength(3);
+  });
+});
+
+describe("draftsStore", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  describe("store structure", () => {
+    it("has all expected methods", () => {
+      expect(typeof draftsStore.loadDrafts).toBe("function");
+      expect(typeof draftsStore.saveDraft).toBe("function");
+      expect(typeof draftsStore.deleteDraft).toBe("function");
+      expect(typeof draftsStore.deleteAllDrafts).toBe("function");
+      expect(typeof draftsStore.formatTimestamp).toBe("function");
+    });
+
+    it("has subscribable stores", () => {
+      expect(typeof draftsStore.drafts.subscribe).toBe("function");
+      expect(typeof draftsStore.isLoading.subscribe).toBe("function");
+    });
+  });
+
+  describe("loadDrafts", () => {
+    it("loads drafts from backend", async () => {
+      const mockDrafts: Draft[] = [
+        makeDraft("draft-1", "Hello world", "2026-01-01T00:00:00+00:00"),
+      ];
+
+      setMockInvokeResult("list_drafts", mockDrafts);
+
+      await draftsStore.loadDrafts();
+
+      expect(invoke).toHaveBeenCalledWith("list_drafts");
+      expect(get(draftsStore.drafts)).toEqual(mockDrafts);
+    });
+
+    it("handles load errors gracefully", async () => {
+      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+      setMockInvokeResult("list_drafts", new Error("Failed to load"));
+
+      await draftsStore.loadDrafts();
+
+      expect(consoleSpy).toHaveBeenCalledWith("Failed to load drafts:", expect.any(Error));
+      consoleSpy.mockRestore();
+    });
+
+    it("sets isLoading during load", async () => {
+      const loadingStates: boolean[] = [];
+      const unsubscribe = draftsStore.isLoading.subscribe((val) => loadingStates.push(val));
+
+      setMockInvokeResult("list_drafts", []);
+      await draftsStore.loadDrafts();
+
+      unsubscribe();
+      expect(loadingStates).toContain(true);
+      expect(loadingStates.at(-1)).toBe(false);
+    });
+  });
+
+  describe("saveDraft", () => {
+    it("saves draft and reloads list", async () => {
+      const mockDraft = makeDraft("new-id", "My draft content", "2026-01-01T00:00:00+00:00");
+
+      setMockInvokeResult("save_draft", mockDraft);
+      setMockInvokeResult("list_drafts", [mockDraft]);
+
+      const result = await draftsStore.saveDraft("My draft content");
+
+      expect(result).toEqual(mockDraft);
+      expect(invoke).toHaveBeenCalledWith("save_draft", { content: "My draft content" });
+    });
+
+    it("returns null on error", async () => {
+      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+      setMockInvokeResult("save_draft", new Error("Save failed"));
+
+      const result = await draftsStore.saveDraft("content");
+
+      expect(result).toBeNull();
+      expect(consoleSpy).toHaveBeenCalledWith("Failed to save draft:", expect.any(Error));
+      consoleSpy.mockRestore();
+    });
+  });
+
+  describe("deleteDraft", () => {
+    it("deletes draft by ID and reloads", async () => {
+      setMockInvokeResult("delete_draft", undefined);
+      setMockInvokeResult("list_drafts", []);
+
+      const result = await draftsStore.deleteDraft("draft-123");
+
+      expect(result).toBe(true);
+      expect(invoke).toHaveBeenCalledWith("delete_draft", { draftId: "draft-123" });
+    });
+
+    it("handles delete errors gracefully", async () => {
+      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+      setMockInvokeResult("delete_draft", new Error("Delete failed"));
+
+      const result = await draftsStore.deleteDraft("draft-123");
+
+      expect(result).toBe(false);
+      expect(consoleSpy).toHaveBeenCalledWith("Failed to delete draft:", expect.any(Error));
+      consoleSpy.mockRestore();
+    });
+  });
+
+  describe("deleteAllDrafts", () => {
+    it("deletes all drafts and clears store", async () => {
+      // First populate the store
+      setMockInvokeResult("list_drafts", [makeDraft("d1", "Draft 1", "2026-01-01T00:00:00+00:00")]);
+      await draftsStore.loadDrafts();
+      expect(get(draftsStore.drafts)).toHaveLength(1);
+
+      setMockInvokeResult("delete_all_drafts", undefined);
+      const result = await draftsStore.deleteAllDrafts();
+
+      expect(result).toBe(true);
+      expect(invoke).toHaveBeenCalledWith("delete_all_drafts");
+      expect(get(draftsStore.drafts)).toHaveLength(0);
+    });
+
+    it("handles delete-all errors gracefully", async () => {
+      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+      setMockInvokeResult("delete_all_drafts", new Error("Delete all failed"));
+
+      const result = await draftsStore.deleteAllDrafts();
+
+      expect(result).toBe(false);
+      expect(consoleSpy).toHaveBeenCalledWith("Failed to delete all drafts:", expect.any(Error));
+      consoleSpy.mockRestore();
+    });
+  });
+
+  describe("formatTimestamp", () => {
+    it("formats a valid ISO timestamp", () => {
+      const result = draftsStore.formatTimestamp("2026-01-15T14:30:00+00:00");
+      // Should produce a human-readable string (locale-dependent)
+      expect(typeof result).toBe("string");
+      expect(result.length).toBeGreaterThan(0);
+    });
+
+    it("falls back to raw string on invalid timestamp", () => {
+      const invalid = "not-a-date";
+      const result = draftsStore.formatTimestamp(invalid);
+      expect(result).toBe(invalid);
+    });
+  });
+});
+
+describe("draft content handling", () => {
+  it("supports content with special characters", () => {
+    const draft = makeDraft(
+      "special",
+      "echo \"Hello\" && echo 'World'",
+      "2026-01-01T00:00:00+00:00"
+    );
+    expect(draft.content).toContain('"');
+    expect(draft.content).toContain("'");
+    expect(draft.content).toContain("&&");
+  });
+
+  it("supports very long content", () => {
+    const longContent = "a".repeat(1000);
+    const draft = makeDraft("long", longContent, "2026-01-01T00:00:00+00:00");
+    expect(draft.content).toHaveLength(1000);
+  });
+});

src/lib/stores/drafts.ts

@@ -0,0 +1,87 @@
+import { writable } from "svelte/store";
+import { invoke } from "@tauri-apps/api/core";
+
+export interface Draft {
+  id: string;
+  content: string;
+  saved_at: string;
+}
+
+function createDraftsStore() {
+  const drafts = writable<Draft[]>([]);
+  const isLoading = writable(false);
+
+  async function loadDrafts(): Promise<void> {
+    isLoading.set(true);
+    try {
+      const list = await invoke<Draft[]>("list_drafts");
+      drafts.set(list);
+    } catch (error) {
+      console.error("Failed to load drafts:", error);
+    } finally {
+      isLoading.set(false);
+    }
+  }
+
+  async function saveDraft(content: string): Promise<Draft | null> {
+    try {
+      const draft = await invoke<Draft>("save_draft", { content });
+      await loadDrafts();
+      return draft;
+    } catch (error) {
+      console.error("Failed to save draft:", error);
+      return null;
+    }
+  }
+
+  async function deleteDraft(draftId: string): Promise<boolean> {
+    try {
+      await invoke("delete_draft", { draftId });
+      await loadDrafts();
+      return true;
+    } catch (error) {
+      console.error("Failed to delete draft:", error);
+      return false;
+    }
+  }
+
+  async function deleteAllDrafts(): Promise<boolean> {
+    try {
+      await invoke("delete_all_drafts");
+      drafts.set([]);
+      return true;
+    } catch (error) {
+      console.error("Failed to delete all drafts:", error);
+      return false;
+    }
+  }
+
+  function formatTimestamp(isoString: string): string {
+    const date = new Date(isoString);
+    if (isNaN(date.getTime())) {
+      return isoString;
+    }
+    try {
+      return date.toLocaleString(undefined, {
+        month: "short",
+        day: "numeric",
+        hour: "numeric",
+        minute: "2-digit",
+      });
+    } catch {
+      return isoString;
+    }
+  }
+
+  return {
+    drafts: { subscribe: drafts.subscribe },
+    isLoading: { subscribe: isLoading.subscribe },
+    loadDrafts,
+    saveDraft,
+    deleteDraft,
+    deleteAllDrafts,
+    formatTimestamp,
+  };
+}
+
+export const draftsStore = createDraftsStore();