feat: implement Undo/Redo/Timeline and Fork Features and fixed opencode.json reading issue on broken json (#99)

* feat: add /undo, /redo, /timeline slash commands and fork button

- Add /undo command to revert to previous user message
- Add /redo command to redo previously undone messages
- Add /timeline command to show conversation history
- Add fork button on user messages (hover) to create new session
- Add TimelineDialog component for navigating conversation history
- Show undo/redo/timeline in autocomplete when session exists
- Fix fork to use SDK session.fork API
- Silent no-op behavior for undo/redo when no messages (matches OpenCode CLI)

* fix: correct fork session endpoint and session switching

- Add hybrid SDK approach using v1 for existing methods and v2 for fork only
- v2 SDK has correct endpoint /session/{sessionID}/fork instead of broken /session/{id}/fork
- Fix forkFromMessage to use setCurrentSession instead of direct set
- Ensures both useSessionStore and useSessionManagementStore are consistent
- Fixes issue where forked sessions appeared empty until sending a new message

* fix: use direct fetch for fork to avoid v2 SDK build errors

- Remove v2 SDK imports and hybrid SDK approach
- Use direct fetch() call to /api/session/{sessionID}/fork endpoint
- Avoids type conflicts between v1 and v2 SDK
- Bypasses broken v1 SDK fork endpoint (wrong path parameter)
- All codebase now uses v1 SDK consistently

* fix: use jsonc-parser for config file parsing

- Replace strip-json-comments + JSON.parse with jsonc-parser
- Handles comments, trailing commas, and unquoted keys
- Matches OpenCode CLI config parsing behavior
- Fixes SyntaxError when reading global opencode.json config

* feat: improve timeline dialog with loading state and search

- Add loading spinner on fork button during operation (~30s on big sessions)
- Refresh session list after fork so new session appears in sidebar immediately
- Add search bar to filter messages by prompt text content
- Show 'No messages found' when search has no results
- Disable fork button while forking to prevent duplicate operations

packages/ui/src/components/chat/ChatMessage.tsx

@@ -578,12 +578,19 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
     }, [messageTextContent]);
 
     const revertToMessage = useSessionStore((state) => state.revertToMessage);
+    const forkFromMessage = useSessionStore((state) => state.forkFromMessage);
 
     const handleRevert = React.useCallback(() => {
         if (!sessionId || !message.info.id) return;
         revertToMessage(sessionId, message.info.id);
     }, [sessionId, message.info.id, revertToMessage]);
 
+    // NEW: Fork handler
+    const handleFork = React.useCallback(() => {
+        if (!sessionId || !message.info.id) return;
+        forkFromMessage(sessionId, message.info.id);
+    }, [sessionId, message.info.id, forkFromMessage]);
+
     const handleToggleTool = React.useCallback((toolId: string) => {
         setExpandedTools((prev) => {
             const next = new Set(prev);
@@ -788,6 +795,7 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
                                         onAuxiliaryContentComplete={handleAuxiliaryContentComplete}
                                         agentMention={agentMention}
                                         onRevert={handleRevert}
+                                        onFork={isUser ? handleFork : undefined}
                                         errorMessage={assistantErrorText}
                                     />
                                 </div>