[Routine - VT] fix: set up FileSystemWatchers for scopes added after workspace folder change

[winterdrive]

Pre-flight Check

Active branches / open PRs checked before this fix:

• origin/routine/vt-fix-duplicate-scope-260625 (PR [Routine - VT] fix: preserve sourceScopeId when duplicating a group #67) — touches src/commands.ts, src/core/DropUriParser.ts, src/dragAndDrop.ts, src/provider.ts
• origin/fix/issue-60-folder-drop-files-mime — touches src/core/DropUriParser.ts, src/dragAndDrop.ts, src/provider.ts

This PR only modifies src/extension.ts, which is untouched by all active branches — no conflicts.

Changes

File: src/extension.ts

When onDidChangeWorkspaceFolders fires, provider.reinitializeScopes() correctly refreshes provider.configScopes with newly added workspace folders. However, setupWatchers() was only called once at extension activation — new scopes had no FileSystemWatcher monitoring their virtualTab.json. Externally-edited config files in dynamically added folders would not auto-refresh the tree view.

Fix: After reinitializeScopes(), filter provider.configScopes to find scopes that don't yet have a watcher, and call setupWatchers only for those new scopes. A Set<string> (watchedScopeIds) tracks which scope IDs already have watchers to prevent duplicate registrations.

+    const watchedScopeIds = new Set<string>(provider.configScopes.map(s => s.id));

     context.subscriptions.push(
         vscode.workspace.onDidChangeWorkspaceFolders(() => {
             provider.reinitializeScopes();
+            const newScopes = provider.configScopes.filter(s => !watchedScopeIds.has(s.id));
+            if (newScopes.length > 0) {
+                setupWatchers(newScopes, provider, context);
+                newScopes.forEach(s => watchedScopeIds.add(s.id));
+            }
         })
     );

Safety Verification

• tsc --noEmit: No errors.
• npm test: 473/473 tests pass. The 1 suite-level failure is a pre-existing TypeScript symbol collision between two git worktrees (busy-yalow-edb734 and trusting-vaughan-0206eb) — unrelated to this change.
• No package.json commands, configuration keys, or serialization format changed.

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