feat: add triggers to all 38 skill templates

Multi-word, skill-specific trigger keywords for GBrain's RESOLVER.md
router. Each skill gets 3-6 triggers derived from its "Use when asked
to..." description text. Avoids single generic words that would collide
across skills (e.g., "debug this" not "debug").

These are distinct from voice-triggers (speech-to-text aliases) and
serve GBrain's checkResolvable() validation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

contrib/add-host/SKILL.md.tmpl

@@ -3,6 +3,10 @@ name: gstack-contrib-add-host
 description: |
   Contributor-only skill: create a new host config for gstack's multi-host system.
   NOT installed for end users. Only usable from the gstack source repo.
+triggers:
+  - add new host
+  - create host config
+  - contribute new agent host
 ---
 
 # /gstack-contrib-add-host — Add a New Host