* fix(files): refresh open file content after external edits
Previously, opening a file in the Files view and then editing it externally
(e.g. via CLI or another editor) would show stale content. Even closing and
reopening the file returned cached content — a full page reload was required.
Root causes:
1. The in-memory readFile cache used path-only hits, with no metadata
validation. External edits were invisible until the cache was evicted.
2. No polling mechanism existed to detect external changes to the open file.
Fix:
- Add mtimeMs to statFile across all runtimes (web, VS Code, desktop).
- Cache layer (RuntimeAPIProvider): validate cache hits against current stat
metadata (mtimeMs + size). On miss, use stat→read→stat to avoid TOCTOU.
- UI layer (FilesView): poll the open file every 2s; on detected change, set
loadedFilePath=null to trigger the existing load effect once (no double
reload). Skip polling when tab is hidden or editor has unsaved changes.
- After save, refresh the stat ref so the next poll doesn't see a spurious
change from the save itself.
Addresses review feedback from PR #827 (double reload + TOCTOU).
* fix(files): address P2 review findings
- readFreshFile retry now uses stat→read→stat to maintain TOCTOU
protection during the retry path (not just the initial read).
- Replace isDirty in polling effect deps with isDirtyRef to avoid
unnecessary interval teardown/restart on every edit/save cycle.
jwcrystal
2f5912c287