feat(curator): background skill maintenance (issue #7816)

Adds the Curator — an auxiliary-model background task that periodically
reviews AGENT-CREATED skills and keeps the collection tidy: tracks usage,
transitions unused skills through active → stale → archived, and spawns
a forked AIAgent to consolidate overlaps and patch drift.

Default: enabled, inactivity-triggered (no cron daemon). Runs on CLI
startup and gateway boot when the last run is older than interval_hours
(default 24) AND the agent has been idle for min_idle_hours (default 2).

Invariants (all load-bearing):
- Never touches bundled or hub-installed skills (.bundled_manifest +
  .hub/lock.json double-filter)
- Never auto-deletes — archive only. Archives are recoverable
  via `hermes curator restore <skill>`
- Pinned skills bypass all auto-transitions
- Uses the aux client; never touches the main session's prompt cache

New files:
- tools/skill_usage.py — sidecar .usage.json telemetry, atomic writes,
  provenance filter
- agent/curator.py — orchestrator: config, idle gating, state-machine
  transitions (pure, no LLM), forked-agent review prompt
- hermes_cli/curator.py — `hermes curator {status,run,pause,resume,
  pin,unpin,restore}` subcommand
- tests/tools/test_skill_usage.py — 29 tests
- tests/agent/test_curator.py — 25 tests

Modified files (surgical patches):
- tools/skills_tool.py — bump view_count on successful skill_view
- tools/skill_manager_tool.py — bump patch_count on skill_manage
  patch/edit/write_file/remove_file; forget record on delete
- hermes_cli/config.py — add curator: section to DEFAULT_CONFIG
- hermes_cli/commands.py — add /curator CommandDef with subcommands
- hermes_cli/main.py — register `hermes curator` subparser via
  register_cli() from hermes_cli.curator
- cli.py — /curator slash-command dispatch + startup hook
- gateway/run.py — gateway-boot hook (mirrors CLI)

Validation:
- 54 new tests across skill_usage + curator, all passing in 3s
- 346 tests across all touched files' neighbors green
- 2783 tests across hermes_cli/ + gateway/test_run_progress_topics.py green
- CLI smoke: `hermes curator status/pause/resume` work end-to-end

Companion to PR #16026 (class-first skill review prompt) — together
they form a loop: the review prompt stops near-duplicate skill creation
at the source, and the curator prunes/consolidates what still accumulates.

Refs #7816.

tools/skill_manager_tool.py

@@ -700,6 +700,17 @@ def skill_manage(
             clear_skills_system_prompt_cache(clear_snapshot=True)
         except Exception:
             pass
+        # Curator telemetry: bump patch_count on edit/patch/write_file (the actions
+        # that mutate an existing skill's guidance), drop the record on delete.
+        # Best-effort; telemetry failures never break the tool.
+        try:
+            from tools.skill_usage import bump_patch, forget
+            if action in ("patch", "edit", "write_file", "remove_file"):
+                bump_patch(name)
+            elif action == "delete":
+                forget(name)
+        except Exception:
+            pass
 
     return json.dumps(result, ensure_ascii=False)