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>

context-save/SKILL.md

@@ -2,14 +2,7 @@
 name: context-save
 preamble-tier: 2
 version: 1.0.0
-description: |
-  Save working context. Captures git state, decisions made, and remaining work
-  so any future session can pick up without losing a beat.
-  Use when asked to "save progress", "save state", "context save", or
-  "save my work". Pair with /context-restore to resume later.
-  Formerly /checkpoint — renamed because Claude Code treats /checkpoint as a
-  native rewind alias in current environments, which was shadowing this skill.
-  (gstack)
+description: Save working context. (gstack)
 allowed-tools:
   - Bash
   - Read
@@ -26,6 +19,16 @@ triggers:
 <!-- AUTO-GENERATED from SKILL.md.tmpl — do not edit directly -->
 <!-- Regenerate: bun run gen:skill-docs -->
 
+
+## When to invoke this skill
+
+Captures git state, decisions made, and remaining work
+so any future session can pick up without losing a beat.
+Use when asked to "save progress", "save state", "context save", or
+"save my work". Pair with /context-restore to resume later.
+Formerly /checkpoint — renamed because Claude Code treats /checkpoint as a
+native rewind alias in current environments, which was shadowing this skill.
+
 ## Preamble (run first)
 
 ```bash