Multiple webview panels can be opened for the same worktree causing race conditions

[SunYanbox]

Description

openWorktreeWebview() in src/worktreeWebview.ts creates a new webview panel on every invocation (line 450-455) with no deduplication:

const panel = vscode.window.createWebviewPanel(
  'quickPrWorktreeDetail',
  `Worktree: ${info.branchName}`,
  { viewColumn: vscode.ViewColumn.Active, preserveFocus: true },
  { enableScripts: true, localResourceRoots: [], retainContextWhenHidden: true },
);

This leads to:

1. Duplicate tabs — clicking "Open" on the same worktree multiple times creates multiple identical panels
2. Stale data in old panels — if the user commits in panel A, panel B still shows old data with no notification
3. Race conditions — simultaneous commits from two panels for the same worktree:
   • Files may be copied twice
   • Commit messages may overwrite each other
   • worktrees.json may experience concurrent write conflicts (though Node.js single-threaded nature mitigates this somewhat)

Affected Code

• src/worktreeWebview.ts:450-455 — unconditional panel creation
• src/worktreeManager.ts — updateWorktree / addWorktree have no locking

Suggested Solution

1. Panel reuse — maintain a Map<string, vscode.WebviewPanel> keyed by worktreeId. If a panel already exists for this worktree, call panel.reveal() instead of creating a new one
2. Clean up on dispose — remove the mapping when panel.onDidDispose fires
3. Always refresh on reveal — before revealing an existing panel, re-fetch worktree data and rebuild the HTML
4. (Optional) Operation lock — add a simple mutex per worktree ID to prevent concurrent commit/finalize/delete operations

Priority

Low. Real-world users rarely open multiple panels for the same worktree, but when it happens the bugs are hard to diagnose.