Add file system watcher for reactive sidebar updates

[Copilot]

What does this PR do?

The sidebar file explorer doesn't react to external filesystem changes — files created, deleted, or renamed outside the app (terminal, other editors) are invisible until manual refresh or restart.

Adds a notify-based file watcher on the Rust backend that emits debounced Tauri events to the frontend on structural changes (create/remove/rename). The frontend listens and auto-refreshes the file tree.

Backend (src-tauri/):

• watcher.rs — FileWatcherState wrapping notify::RecommendedWatcher with 300ms debounce via AtomicBool + timer thread. Only fires on structural events (create/remove/rename), not content modifications.
• commands.rs — watch_workspace / unwatch_workspace Tauri commands
• lib.rs — Registers FileWatcherState as managed state
• Cargo.toml — Added notify = "6", tempfile = "3" (dev, fixes pre-existing test gap)

Frontend (src/):

• hooks/useFileWatcher.ts — Starts watcher on workspace load, listens for "workspace-changed" events, triggers refresh with concurrent-call guard
• App.tsx — Wires up useFileWatcher()

// watcher.rs — event filter: only structural changes trigger sidebar refresh
let is_structural_change = matches!(
    event.kind,
    EventKind::Create(_) | EventKind::Remove(_)
        | EventKind::Modify(notify::event::ModifyKind::Name(_))
);

Merge conflict resolution:

• Merged origin/main into PR branch to resolve conflicts with the search feature (search_workspace command, SearchPanel component, and related changes in commands.rs, lib.rs, and App.tsx)
• Resolved App.tsx conflict from main's single-quote style migration; updated useFileWatcher.ts to match project's new Prettier config (singleQuote: true)

Related issue

Checklist

• I tested my changes
• I didn't break existing functionality
• I followed repo style

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[7sg56]

@copilot there are conflicts

[Copilot]

@copilot there are conflicts

Resolved in 179ce0e. Merged origin/main into the PR branch — the conflicts were in commands.rs (duplicate SearchResult struct + search_workspace function from the search feature) and lib.rs (overlapping invoke handler registrations). Both files now include both the search feature and the file watcher additions. Build, tests, lint, and typecheck all pass.

[7sg56]

There exists conflict.tsx @copilot

[7sg56]

fix the conflicts @copilot

[Copilot]

fix the conflicts @copilot

Resolved in 7a52e59. Merged origin/main into the PR branch — the conflict was in src/App.tsx where main switched to single-quote imports. Also updated useFileWatcher.ts to match the project's new single-quote Prettier config. Typecheck and lint both pass.