feat(catalog): T4 — catalog trim + proactive-suggestions.json (Phase A.4)

Shortens frontmatter `description:` in every Claude SKILL.md to a single
lead sentence + (gstack) tag. The routing prose ("Use when asked to...",
"Proactively suggest...") and voice triggers move to a "## When to invoke"
body section so they remain discoverable inside the skill. A per-run
registry at scripts/proactive-suggestions.json aggregates the routing/
voice text for all 52 skills so agents can pull guidance on demand
without paying for it in the always-loaded catalog.

Build flag --catalog-mode=full restores v1.44 legacy behavior (full
multi-line descriptions in frontmatter). Default is trim.

splitCatalogDescription() extracts: lead sentence, routing paragraphs,
voice-triggers line, (gstack) tag presence. Short descriptions (<120
chars, already trimmed) are skipped via a guard so re-runs are idempotent.

Measured impact (vs v1.44.1 baseline):
- Catalog tokens (sum of description bytes / 4): 9,319 → 4,045  (-56.6%)
- Total SKILL.md corpus bytes:                   2,915 KB → 2,880 KB (-1.2%)
- Routing prose preserved as in-skill "## When to invoke" sections
- 52 skill entries in scripts/proactive-suggestions.json (on-demand registry)

The corpus drop is small because catalog trim MOVES text from frontmatter
to body, it doesn't delete it. The headline win is the catalog: the
always-loaded system prompt surface drops by more than half.

Test plan:
- bun test test/gen-skill-docs.test.ts: 389 pass, 0 fail
- Manual: ship/SKILL.md frontmatter description is now ONE line ending
  with `(gstack)`; allowed-tools field on next line (YAML well-formed)
- Manual: scripts/proactive-suggestions.json contains 52 entries
- bun run gen:skill-docs --catalog-mode=full restores legacy behavior

53 files changed (52 SKILL.md across hosts + the new proactive-suggestions.json).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

sync-gbrain/SKILL.md

@@ -2,13 +2,7 @@
 name: sync-gbrain
 preamble-tier: 2
 version: 1.0.0
-description: |
-  Keep gbrain current with this repo's code and refresh agent search
-  guidance in CLAUDE.md. Wraps the gstack-gbrain-sync orchestrator with
-  state probing, native code-surface registration, capability checks,
-  and a verdict block. Re-runnable, idempotent. Use when: "sync gbrain",
-  "refresh gbrain", "re-index this repo", "gbrain search isn't finding
-  things". (gstack)
+description: Keep gbrain current with this repo's code and refresh agent search guidance in CLAUDE.md. Wraps the gstack-gbrain-sync orchestrator with state (gstack)
 triggers:
   - sync gbrain
   - refresh gbrain
@@ -26,6 +20,14 @@ allowed-tools:
 <!-- AUTO-GENERATED from SKILL.md.tmpl — do not edit directly -->
 <!-- Regenerate: bun run gen:skill-docs -->
 
+
+## When to invoke this skill
+
+probing, native code-surface registration, capability checks,
+and a verdict block. Re-runnable, idempotent. Use when: "sync gbrain",
+"refresh gbrain", "re-index this repo", "gbrain search isn't finding
+things".
+
 ## Preamble (run first)
 
 ```bash