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/message/MessageBody.tsx

@@ -16,7 +16,7 @@ import { isEmptyTextPart, extractTextContent } from './partUtils';
 import { FadeInOnReveal } from './FadeInOnReveal';
 import { Button } from '@/components/ui/button';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip';
-import { RiCheckLine, RiFileCopyLine, RiChatNewLine, RiArrowGoBackLine } from '@remixicon/react';
+import { RiCheckLine, RiFileCopyLine, RiChatNewLine, RiArrowGoBackLine, RiGitBranchLine } from '@remixicon/react';
 import { ArrowsMerge } from '@/components/icons/ArrowsMerge';
 import type { ContentChangeReason } from '@/hooks/useChatScrollManager';
 
@@ -133,6 +133,7 @@ interface MessageBodyProps {
     agentMention?: AgentMentionInfo;
     turnGroupingContext?: TurnGroupingContext;
     onRevert?: () => void;
+    onFork?: () => void;
     errorMessage?: string;
 }
 
@@ -147,7 +148,8 @@ const UserMessageBody: React.FC<{
     onShowPopup: (content: ToolPopupContent) => void;
     agentMention?: AgentMentionInfo;
     onRevert?: () => void;
-}> = ({ messageId, parts, isMobile, hasTouchInput, hasTextContent, onCopyMessage, copiedMessage, onShowPopup, agentMention, onRevert }) => {
+    onFork?: () => void;
+}> = ({ messageId, parts, isMobile, hasTouchInput, hasTextContent, onCopyMessage, copiedMessage, onShowPopup, agentMention, onRevert, onFork }) => {
     const [copyHintVisible, setCopyHintVisible] = React.useState(false);
     const copyHintTimeoutRef = React.useRef<number | null>(null);
 
@@ -239,7 +241,7 @@ const UserMessageBody: React.FC<{
                 })}
             </div>
             <MessageFilesDisplay files={parts} onShowPopup={onShowPopup} />
-            {(canCopyMessage && hasCopyableText) || onRevert ? (
+            {(canCopyMessage && hasCopyableText) || onRevert || onFork ? (
                 <div className={cn(
                     "mt-1 flex items-center justify-end gap-2 opacity-0 pointer-events-none transition-opacity duration-150 group-hover/message:opacity-100 group-hover/message:pointer-events-auto focus-within:opacity-100 focus-within:pointer-events-auto",
                     copyHintVisible && "opacity-100 pointer-events-auto"
@@ -265,6 +267,26 @@ const UserMessageBody: React.FC<{
                             <TooltipContent sideOffset={6}>Revert from here</TooltipContent>
                         </Tooltip>
                     )}
+                    {onFork && (
+                        <Tooltip delayDuration={1000}>
+                            <TooltipTrigger asChild>
+                                <Button
+                                    type="button"
+                                    variant="ghost"
+                                    size="icon"
+                                    className="h-8 w-8 text-muted-foreground bg-transparent hover:text-foreground hover:!bg-transparent active:!bg-transparent focus-visible:!bg-transparent focus-visible:ring-2 focus-visible:ring-primary/50"
+                                    onPointerDown={(event) => event.stopPropagation()}
+                                    onClick={(event) => {
+                                        event.stopPropagation();
+                                        onFork();
+                                    }}
+                                >
+                                    <RiGitBranchLine className="h-3.5 w-3.5" />
+                                </Button>
+                            </TooltipTrigger>
+                            <TooltipContent sideOffset={6}>Fork from here</TooltipContent>
+                        </Tooltip>
+                    )}
                     {canCopyMessage && hasCopyableText && (
                         <Tooltip delayDuration={1000}>
                             <TooltipTrigger asChild>
@@ -1226,6 +1248,7 @@ const MessageBody: React.FC<MessageBodyProps> = ({ isUser, ...props }) => {
                 onShowPopup={props.onShowPopup}
                 agentMention={props.agentMention}
                 onRevert={props.onRevert}
+                onFork={props.onFork}
             />
         );
     }