[BUG] Agents in .claude/agents/ not auto-loaded without restart (Windows, Desktop app)

Related to #5738 (closed as completed) and #23608 (closed as duplicate) — reopening as a fresh report because the watcher behavior described as fixed there doesn't reproduce here, on a different platform/client combination.

Additional data point: Windows + Desktop app, none of the documented exceptions apply

Environment

• Claude Code version: 2.1.204
• Platform: Windows 11 Pro (10.0.26200)
• Client: Claude desktop app (Code tab), not the terminal CLI

Reproduction

1. .claude/agents/ already existed with two working subagents (rls-checker.md, authz-auditor.md), confirmed invocable as subagent_type from a previous session.
2. Mid-session, added a third file (schema-guardian.md) to that same pre-existing directory, valid frontmatter matching the working agents exactly.
3. It did not appear as an available subagent_type. No --add-dir, no --disable-slash-commands — normal interactive session.
4. Only appeared after an explicit session restart (New agent types are now available for the Agent tool).
5. Repeated with a fourth file (doc-cross-checker.md) — same result.

Expected per docs: "reloads changes within seconds (no restart needed in most cases)." None of the three documented exceptions apply here, so this looks like either an undocumented fourth case or the watcher not working reliably on Windows / the desktop app client specifically.