feat: major feature additions and improvements (#135)

## Summary

This PR includes major feature additions, bug fixes, comprehensive testing improvements, and responsive design enhancements!

## New Features ✨

### Plugin & MCP Management (#133, #134)
- **Plugin Management Panel**: Install, uninstall, enable/disable, and update plugins
- **MCP Server Management Panel**: Add/remove MCP servers, view detailed configuration
- **Marketplace Management**: Add/remove plugin marketplaces from GitHub
- Backend commands for full CLI integration (`list_plugins`, `install_plugin`, `add_mcp_server`, etc.)
- Beautiful UI with proper loading states, error handling, and theme support

### Visual Todo List Panel (#132)
- Real-time todo list display when Hikari uses the `TodoWrite` tool
- Shows pending/in-progress/completed status with visual indicators
- Progress bar and completion count
- Automatically clears on disconnect
- Theme-aware styling

### Clear Session History Button (#130)
- "Clear All Sessions" button in Session History panel
- Confirmation dialog with session count
- Keyboard support and accessibility features
- Gives users control over disk usage

### CLI Version Display (#131)
- Displays Claude CLI version in status bar
- Auto-polls every 30 seconds for updates
- Useful for debugging and feature compatibility

## Bug Fixes 🐛

### Stats Panel Scrolling (#136)
- **Fixed stats panel overflow**: Added scrollable container with `max-height` constraint
- Stats panel now scrolls when content (Tools Used, Historical Costs, Budget sections) gets too long
- Prevents content from overflowing off screen

### Agent Monitor Fixes (#122)
- **Fixed agents stuck in "running" state**: Added `SubagentStop` hook parsing
- **Fixed agents persisting after disconnect**: Call `clearConversation()` on disconnect
- **Fixed "Kill All" button**: Now properly marks all agents as errored
- **Fixed badge persisting after tab close**: Cleanup agents when conversation is deleted
- Comprehensive tests for agent lifecycle management

### Discord RPC Cleanup (#129)
- Removed file-based logging for Discord RPC
- Replaced with proper `tracing` framework usage
- Reduces disk usage and eliminates maintenance burden

### Close Modal Bug Fix (#128)
- Fixed close confirmation modal not triggering after Discord RPC refactor
- Removed frontend calls to deleted `log_discord_rpc` command
- Modal now works correctly after all operations

### Responsive Design Fixes (#118)
- Fixed top navigation icons getting cut off at small screen widths
- Fixed Connect button disappearing on narrow screens
- Fixed bottom status info (clock, CLI version) getting cut off
- Added flex-wrap and mobile-optimised layouts
- Icons-only mode on screens < 640px
- Vertical stacking on screens < 768px

## Testing Improvements 🧪

### Comprehensive Test Coverage (#114)
- **417 backend tests** (up from 408)
- **387 frontend tests** (up from 363)
- **61%+ backend code coverage**
- Added E2E integration tests for cross-platform notification commands
- New test files: `agents.test.ts`, comprehensive CLI parsing tests
- Tests for `debug_logger.rs`, `bridge_manager.rs`, `notifications.rs`
- Console mocking for cleaner test output
- Fixed flaky frontend tests

### Testing Documentation
- Updated CLAUDE.md with comprehensive testing guidelines
- Documented mocking approaches (console mocking, E2E command structure testing)
- Added step-by-step guide for adding tests to new features
- Goal to maintain ~100% test coverage documented

## Closes

Closes #114
Closes #118
Closes #122
Closes #128
Closes #129
Closes #130
Closes #131
Closes #132
Closes #133
Closes #134
Closes #136

## Technical Details

- All new backend commands properly registered in `lib.rs`
- CLI output parsing with comprehensive test coverage
- Cross-platform compatibility verified through E2E tests (Linux CI can test Windows commands)
- Theme-aware UI components using CSS variables throughout
- Proper TypeScript types for all new stores and components
- ESLint and Prettier compliant
- All Clippy warnings addressed

✨ This PR was created with help from Hikari~ 🌸

Reviewed-on: #135
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src/lib/components/SessionHistoryPanel.svelte

@@ -15,9 +15,23 @@
   let showDeleteConfirm = $state<string | null>(null);
   let showExportMenu = $state<string | null>(null);
   let isImporting = $state(false);
+  let showClearAllConfirm = $state(false);
 
-  const sessions = $derived(sessionsStore.sessions);
-  const isLoading = $derived(sessionsStore.isLoading);
+  let sessions = $state<SessionListItem[]>([]);
+  let isLoading = $state(false);
+
+  $effect(() => {
+    const unsubSessions = sessionsStore.sessions.subscribe((value) => {
+      sessions = value;
+    });
+    const unsubLoading = sessionsStore.isLoading.subscribe((value) => {
+      isLoading = value;
+    });
+    return () => {
+      unsubSessions();
+      unsubLoading();
+    };
+  });
 
   onMount(() => {
     sessionsStore.loadSessions();
@@ -121,6 +135,11 @@
     }
   }
 
+  async function handleClearAll(): Promise<void> {
+    await sessionsStore.clearAllSessions();
+    showClearAllConfirm = false;
+  }
+
   function toggleExportMenu(sessionId: string): void {
     if (showExportMenu === sessionId) {
       showExportMenu = null;
@@ -186,6 +205,22 @@
             </svg>
             {isImporting ? "Importing..." : "Import"}
           </button>
+          <button
+            onclick={() => (showClearAllConfirm = true)}
+            disabled={sessions.length === 0}
+            class="px-3 py-1.5 text-sm font-medium bg-red-500/10 text-red-500 border border-red-500/30 rounded hover:bg-red-500/20 transition-colors disabled:opacity-50 disabled:cursor-not-allowed flex items-center gap-2"
+            title="Clear all sessions"
+          >
+            <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path
+                stroke-linecap="round"
+                stroke-linejoin="round"
+                stroke-width="2"
+                d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
+              />
+            </svg>
+            Clear All
+          </button>
         {/if}
         <button
           onclick={onClose}
@@ -281,11 +316,11 @@
       </div>
 
       <div class="overflow-y-auto flex-1">
-        {#if $isLoading}
+        {#if isLoading}
           <div class="flex items-center justify-center p-8">
             <div class="text-[var(--text-tertiary)]">Loading sessions...</div>
           </div>
-        {:else if $sessions.length === 0}
+        {:else if sessions.length === 0}
           <div class="flex flex-col items-center justify-center p-8 text-center">
             <svg
               class="w-16 h-16 text-[var(--text-tertiary)] mb-4"
@@ -307,7 +342,7 @@
           </div>
         {:else}
           <div class="divide-y divide-[var(--border-color)]">
-            {#each $sessions as session (session.id)}
+            {#each sessions as session (session.id)}
               <div class="p-4 hover:bg-[var(--bg-secondary)] transition-colors group">
                 <div class="flex items-start justify-between gap-4">
                   <button class="flex-1 text-left" onclick={() => handleViewSession(session)}>
@@ -428,6 +463,62 @@
   </div>
 </div>
 
+{#if showClearAllConfirm}
+  <div
+    class="fixed inset-0 bg-black/50 backdrop-blur-sm z-[60] flex items-center justify-center p-4"
+    onclick={() => (showClearAllConfirm = false)}
+    role="button"
+    tabindex="0"
+    onkeydown={(e) => e.key === "Escape" && (showClearAllConfirm = false)}
+  >
+    <div
+      class="bg-[var(--bg-primary)] border border-red-500/30 rounded-lg shadow-xl max-w-md w-full p-6"
+      onclick={(e) => e.stopPropagation()}
+      role="dialog"
+      aria-labelledby="clear-all-title"
+      aria-describedby="clear-all-description"
+      tabindex="-1"
+    >
+      <div class="flex items-start gap-4">
+        <div class="flex-shrink-0 text-red-500">
+          <svg class="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path
+              stroke-linecap="round"
+              stroke-linejoin="round"
+              stroke-width="2"
+              d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z"
+            />
+          </svg>
+        </div>
+        <div class="flex-1">
+          <h3 id="clear-all-title" class="text-lg font-semibold text-[var(--text-primary)] mb-2">
+            Clear All Sessions?
+          </h3>
+          <p id="clear-all-description" class="text-[var(--text-secondary)] mb-4">
+            This will permanently delete all {sessions.length} session{sessions.length === 1
+              ? ""
+              : "s"}. This action cannot be undone.
+          </p>
+          <div class="flex justify-end gap-3">
+            <button
+              onclick={() => (showClearAllConfirm = false)}
+              class="px-4 py-2 text-sm font-medium bg-[var(--bg-secondary)] text-[var(--text-primary)] border border-[var(--border-color)] rounded hover:bg-[var(--bg-tertiary)] transition-colors"
+            >
+              Cancel
+            </button>
+            <button
+              onclick={handleClearAll}
+              class="px-4 py-2 text-sm font-medium bg-red-500 text-white rounded hover:bg-red-600 transition-colors"
+            >
+              Clear All Sessions
+            </button>
+          </div>
+        </div>
+      </div>
+    </div>
+  </div>
+{/if}
+
 <style>
   [role="dialog"] {
     animation: slideIn 0.2s ease-out;