feat: add full-text search across conversations (#482)

* feat: add full-text search across conversations in sidebar

Add a search mode toggle (Projects/Conversations) to the sidebar search bar.
In Conversations mode, search text content across all JSONL session files
with debounced API calls, highlighted snippets, and click-to-navigate results.

* fix: address PR review feedback - session summary tracking, search sequence invalidation, fallback navigation, SSE streaming

- Track session summaries per-session in a Map instead of file-scoped variable
- Increment searchSeqRef when clearing conversation search to invalidate in-flight requests
- Add fallback session navigation when session not loaded in sidebar paging
- Stream search results via SSE for progressive display with progress indicator

* feat(search): add Codex/Gemini search and scroll-to-message navigation

- Search now includes Codex sessions (JSONL from ~/.codex/sessions/) and
  Gemini sessions (in-memory via sessionManager) in addition to Claude
- Search results include provider info and display a provider badge
- Click handler resolves the correct provider instead of hardcoding claude
- Clicking a search result loads all messages and scrolls to the matched
  message with a highlight flash animation

* fix(search): Codex search path matching and scroll reliability

- Fix Codex search scanning all sessions for every project by checking
  session_meta cwd match BEFORE scanning messages (was inflating match
  count and hitting limit before reaching later projects)
- Fix Codex search missing user messages in response_item entries
  (role=user with input_text content parts)
- Fix scroll-to-message being overridden by initial scrollToBottom
  using searchScrollActiveRef to inhibit competing scroll effects
- Fix snippet matching using contiguous substring instead of
  filtered words (which created non-existent phrases)

* feat(search): add Gemini CLI session support for search and history viewing

Gemini CLI sessions stored in ~/.gemini/tmp/<project>/chats/*.json are now
indexed for conversation search and can be loaded for viewing. Previously
only sessions created through the UI (sessionManager) were searchable.

* fix(search): full-word matching and longer highlight flash

- Search now uses word boundaries (\b) instead of substring matching,
  so "hi" no longer matches "this"
- Highlight flash extended to 4s with thicker outline and subtle
  background tint for better visibility

src/components/sidebar/view/Sidebar.tsx

@@ -60,6 +60,12 @@ function Sidebar({
     editingSession,
     editingSessionName,
     searchFilter,
+    searchMode,
+    setSearchMode,
+    conversationResults,
+    isSearching,
+    searchProgress,
+    clearConversationResults,
     deletingProjects,
     deleteConfirmation,
     sessionDeleteConfirmation,
@@ -220,6 +226,37 @@ function Sidebar({
             searchFilter={searchFilter}
             onSearchFilterChange={setSearchFilter}
             onClearSearchFilter={() => setSearchFilter('')}
+            searchMode={searchMode}
+            onSearchModeChange={(mode: 'projects' | 'conversations') => {
+              setSearchMode(mode);
+              if (mode === 'projects') clearConversationResults();
+            }}
+            conversationResults={conversationResults}
+            isSearching={isSearching}
+            searchProgress={searchProgress}
+            onConversationResultClick={(projectName: string, sessionId: string, provider: string, messageTimestamp?: string | null, messageSnippet?: string | null) => {
+              const resolvedProvider = (provider || 'claude') as SessionProvider;
+              const project = projects.find(p => p.name === projectName);
+              const searchTarget = { __searchTargetTimestamp: messageTimestamp || null, __searchTargetSnippet: messageSnippet || null };
+              const sessionObj = {
+                id: sessionId,
+                __provider: resolvedProvider,
+                __projectName: projectName,
+                ...searchTarget,
+              };
+              if (project) {
+                handleProjectSelect(project);
+                const sessions = getProjectSessions(project);
+                const existing = sessions.find(s => s.id === sessionId);
+                if (existing) {
+                  handleSessionClick({ ...existing, ...searchTarget }, projectName);
+                } else {
+                  handleSessionClick(sessionObj, projectName);
+                }
+              } else {
+                handleSessionClick(sessionObj, projectName);
+              }
+            }}
             onRefresh={() => {
               void refreshProjects();
             }}