feat: project context panel for persistent PROJECT/REQUIREMENTS/ROADMAP/STATE files (#188)

- Add projectContext store with load/save via existing Tauri file commands
- Add ProjectContextPanel modal with tabbed editor, file-exists badges, and templates
- Add injectTextStore signal so StatusBar can inject content directly into InputBar
- Add PROJECT_CONTEXT_SYSTEM_ADDENDUM auto-appended to custom_instructions on connect
- Add open-book button to StatusBar to open the panel
- Add PROJECT.md example file for the hikari-desktop project itself
- 34 tests covering all store methods, exports, and signal behaviour

src/lib/components/InputBar.svelte

@@ -37,6 +37,7 @@
   import DraftPanel from "$lib/components/DraftPanel.svelte";
   import TextInputContextMenu from "$lib/components/TextInputContextMenu.svelte";
   import { draftsStore } from "$lib/stores/drafts";
+  import { injectTextStore } from "$lib/stores/projectContext";
   import type { Attachment } from "$lib/types/messages";
 
   const INPUT_HISTORY_KEY = "hikari-input-history";
@@ -178,6 +179,14 @@
     }
   });
 
+  // Project context injection — set by StatusBar via injectTextStore signal.
+  injectTextStore.subscribe((text) => {
+    if (text === null) return;
+    inputValue = inputValue.trim() ? text + "\n\n" + inputValue : text;
+    userHasTyped = true;
+    injectTextStore.set(null);
+  });
+
   function clearInput() {
     inputValue = "";
     const activeId = get(claudeStore.activeConversationId);