feat: GBrain resolver — brain-first lookup and save-to-brain

New scripts/resolvers/gbrain.ts with two resolver functions:
- GBRAIN_CONTEXT_LOAD: search brain for context before skill starts
- GBRAIN_SAVE_RESULTS: save skill output to brain after completion

Placeholders added to 4 thinking skill templates (office-hours,
investigate, plan-ceo-review, retro). Resolves to empty string on
all hosts except gbrain via suppressedResolvers.

GBRAIN suppression added to all 9 non-gbrain host configs.

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

office-hours/SKILL.md.tmpl

@@ -37,6 +37,8 @@ You are a **YC office hours partner**. Your job is to ensure the problem is unde
 
 ---
 
+{{GBRAIN_CONTEXT_LOAD}}
+
 ## Phase 1: Context Gathering
 
 Understand the project and the area the user wants to change.
@@ -462,7 +464,10 @@ PRIOR=$(ls -t ~/.gstack/projects/$SLUG/*-$BRANCH-design-*.md 2>/dev/null | head
 ```
 If `$PRIOR` exists, the new doc gets a `Supersedes:` field referencing it. This creates a revision chain — you can trace how a design evolved across office hours sessions.
 
-Write to `~/.gstack/projects/{slug}/{user}-{branch}-design-{datetime}.md`:
+Write to `~/.gstack/projects/{slug}/{user}-{branch}-design-{datetime}.md`.
+
+After writing the design doc, tell the user:
+**"Design doc saved to: {full path}. Other skills (/plan-ceo-review, /plan-eng-review) will find it automatically."**
 
 ### Startup mode design doc template:
 
@@ -591,6 +596,8 @@ Present the reviewed design doc to the user via AskUserQuestion:
 - B) Revise — specify which sections need changes (loop back to revise those sections)
 - C) Start over — return to Phase 2
 
+{{GBRAIN_SAVE_RESULTS}}
+
 ---
 
 ## Phase 6: Handoff — The Relationship Closing