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/CommandAutocomplete.tsx

@@ -1,5 +1,5 @@
 import React from 'react';
-import { RiCommandLine, RiFileLine, RiFlashlightLine, RiRefreshLine, RiScissorsLine, RiTerminalBoxLine } from '@remixicon/react';
+import { RiCommandLine, RiFileLine, RiFlashlightLine, RiRefreshLine, RiScissorsLine, RiTerminalBoxLine, RiArrowGoBackLine, RiArrowGoForwardLine, RiTimeLine } from '@remixicon/react';
 import { cn } from '@/lib/utils';
 import { opencodeClient } from '@/lib/opencode/client';
 import { useSessionStore } from '@/stores/useSessionStore';
@@ -29,15 +29,17 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
   onCommandSelect,
   onClose
 }, ref) => {
-  const { hasMessagesInCurrentSession } = useSessionStore(
+  const { hasMessagesInCurrentSession, currentSessionId } = useSessionStore(
     useShallow((state) => {
       const sessionId = state.currentSessionId;
       const messageCount = sessionId ? (state.messages.get(sessionId)?.length ?? 0) : 0;
       return {
         hasMessagesInCurrentSession: messageCount > 0,
+        currentSessionId: sessionId,
       };
     })
   );
+  const hasSession = Boolean(currentSessionId);
 
   const [commands, setCommands] = React.useState<CommandInfo[]>([]);
   const [loading, setLoading] = React.useState(false);
@@ -79,9 +81,18 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
         }));
 
         const builtInCommands: CommandInfo[] = [
-          ...(hasMessagesInCurrentSession
-            ? []
-            : [{ name: 'init', description: 'Create/update AGENTS.md file', isBuiltIn: true }]),
+          ...(hasSession && !hasMessagesInCurrentSession
+            ? [{ name: 'init', description: 'Create/update AGENTS.md file', isBuiltIn: true }]
+            : []
+          ),
+          ...(hasSession  // Show when session exists, not when hasMessages
+            ? [
+                { name: 'undo', description: 'Undo the last message', isBuiltIn: true },
+                { name: 'redo', description: 'Redo previously undone messages', isBuiltIn: true },
+                { name: 'timeline', description: 'Jump to a specific message', isBuiltIn: true },
+              ]
+            : []
+          ),
           { name: 'summarize', description: 'Generate a summary of the current session', isBuiltIn: true },
         ];
 
@@ -114,9 +125,18 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
 
         const allowInitCommand = !hasMessagesInCurrentSession;
         const builtInCommands: CommandInfo[] = [
-          ...(hasMessagesInCurrentSession
-            ? []
-            : [{ name: 'init', description: 'Create/update AGENTS.md file', isBuiltIn: true }]),
+          ...(hasSession && !hasMessagesInCurrentSession
+            ? [{ name: 'init', description: 'Create/update AGENTS.md file', isBuiltIn: true }]
+            : []
+          ),
+          ...(hasSession  // Show when session exists, not when hasMessages
+            ? [
+                { name: 'undo', description: 'Undo the last message', isBuiltIn: true },
+                { name: 'redo', description: 'Redo previously undone messages', isBuiltIn: true },
+                { name: 'timeline', description: 'Jump to a specific message', isBuiltIn: true },
+              ]
+            : []
+          ),
           { name: 'summarize', description: 'Generate a summary of the current session', isBuiltIn: true },
         ];
 
@@ -134,7 +154,7 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
     };
 
     loadCommands();
-  }, [searchQuery, hasMessagesInCurrentSession]);
+  }, [searchQuery, hasMessagesInCurrentSession, hasSession]);
 
   React.useEffect(() => {
     setSelectedIndex(0);
@@ -184,6 +204,12 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
     switch (command.name) {
       case 'init':
         return <RiFileLine className="h-3.5 w-3.5 text-green-500" />;
+      case 'undo':
+        return <RiArrowGoBackLine className="h-3.5 w-3.5 text-orange-500" />;
+      case 'redo':
+        return <RiArrowGoForwardLine className="h-3.5 w-3.5 text-orange-500" />;
+      case 'timeline':
+        return <RiTimeLine className="h-3.5 w-3.5 text-blue-500" />;
       case 'summarize':
         return <RiScissorsLine className="h-3.5 w-3.5 text-purple-500" />;
       case 'test':