feat(brain): brain-aware planning resolvers + 3 new placeholders (T4)

scripts/resolvers/gbrain.ts adds:
  - generateBrainPreflight(ctx)       — emits per-skill ## Brain Context
                                        block + bash that loads digests via
                                        gstack-brain-cache get (one call per
                                        digest). Per-skill subset comes from
                                        SKILL_DIGEST_SUBSETS (single source).
  - generateBrainCacheRefresh(ctx)    — at-skill-end background refresh hook;
                                        non-blocking; warms cache for next run.
  - generateBrainWriteBack(ctx)       — Phase 2 / E5 calibration write-back
                                        with per-skill weight. Gated on
                                        personal trust policy + the
                                        BRAIN_CALIBRATION_WRITEBACK flag.
                                        Includes invalidation bash that busts
                                        affected digests after the write.

scripts/resolvers/index.ts registers three new placeholders:
  {{BRAIN_PREFLIGHT}}, {{BRAIN_CACHE_REFRESH}}, {{BRAIN_WRITE_BACK}}

All three resolvers return empty string for skills not in
SKILL_DIGEST_SUBSETS (defensive — skill template authors can drop the
placeholders into non-preflight skills with zero effect).

D9 privacy is mentioned in the rendered preflight prose so the agent
knows to expect filtered salience.
D11 codex tension: write-back gates on brain_trust_policy@<hash> being
personal — shared brains skip write-back to avoid polluting team
calibration profile.

test/brain-preflight.test.ts: 19 tests covering subset rendering,
non-preflight skill gating, cross-project vs per-project --project flag
emission, weight injection per skill, BRAIN_CALIBRATION_WRITEBACK flag
mention, and registration in RESOLVERS map.

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

scripts/resolvers/index.ts

@@ -30,7 +30,7 @@ import { generateInvokeSkill } from './composition';
 import { generateReviewArmy } from './review-army';
 import { generateDxFramework } from './dx';
 import { generateModelOverlay } from './model-overlay';
-import { generateGBrainContextLoad, generateGBrainSaveResults } from './gbrain';
+import { generateGBrainContextLoad, generateGBrainSaveResults, generateBrainPreflight, generateBrainCacheRefresh, generateBrainWriteBack } from './gbrain';
 import { generateQuestionPreferenceCheck, generateQuestionLog, generateInlineTuneFeedback } from './question-tuning';
 import { generateMakePdfSetup } from './make-pdf';
 import { generateTasksSectionEmit, generateTasksSectionAggregate } from './tasks-section';
@@ -86,6 +86,9 @@ export const RESOLVERS: Record<string, ResolverValue> = {
   BIN_DIR: (ctx) => ctx.paths.binDir,
   GBRAIN_CONTEXT_LOAD: generateGBrainContextLoad,
   GBRAIN_SAVE_RESULTS: generateGBrainSaveResults,
+  BRAIN_PREFLIGHT: generateBrainPreflight,
+  BRAIN_CACHE_REFRESH: generateBrainCacheRefresh,
+  BRAIN_WRITE_BACK: generateBrainWriteBack,
   QUESTION_PREFERENCE_CHECK: generateQuestionPreferenceCheck,
   QUESTION_LOG: generateQuestionLog,
   INLINE_TUNE_FEEDBACK: generateInlineTuneFeedback,