merge: integrate origin/main (v0.18.1.0) into open-agents-learnings

Main moved forward 6 commits while this branch was local. Integrated
both sides preserving all functionality:

From main (v0.16.4.0 → v0.18.1.0):
- v0.17.0.0 — UX behavioral foundations + ux-audit (generateUXPrinciples,
  {{UX_PRINCIPLES}} placeholder, triggers frontmatter on skills)
- v0.18.0.0 — Confusion Protocol, Hermes + GBrain hosts, brain-first
  resolver (generateBrainHealthInstruction, generateConfusionProtocol,
  generateGBrainContextLoad, generateGBrainSaveResults, hosts/gbrain.ts,
  hosts/hermes.ts, scripts/resolvers/gbrain.ts, GBrain bash health check)
- v0.18.0.1 — ngrok Windows build fix
- 0cc830b6 — tilde-in-assignment permission fix
- cc42f14a — gstack compact design doc (tabled)
- 822e843a — headed browser auto-shutdown + disconnect cleanup (v0.18.1.0)

Integration approach: keep this branch's preamble.ts submodule refactor
as the structure of record. Extracted main's two new generators into
their own submodules:
- scripts/resolvers/preamble/generate-brain-health-instruction.ts
- scripts/resolvers/preamble/generate-confusion-protocol.ts

Updated scripts/resolvers/preamble/generate-preamble-bash.ts to absorb
main's GBrain health check (host-conditional on gbrain/hermes).

scripts/resolvers/index.ts now imports BOTH:
- This branch's adds: MODEL_OVERLAY, TASTE_PROFILE, BIN_DIR resolvers
- Main's adds: UX_PRINCIPLES, GBRAIN_CONTEXT_LOAD, GBRAIN_SAVE_RESULTS
  resolvers

scripts/resolvers/design.ts keeps both generateTasteProfile (this
branch) and generateUXPrinciples (main). Sibling exports, no overlap.

scripts/gen-skill-docs.ts keeps both this branch's --model flag wiring
and main's edits.

Templates auto-merged where possible. The 35 generated SKILL.md /
golden conflicts auto-resolved via `bun run gen:skill-docs --host all`
followed by re-snapshotting the ship goldens for claude/codex/factory.

Verification:
- bun run gen:skill-docs --host all completes cleanly
- bun test: 1 pre-existing failure (gstack-community-dashboard Supabase
  network test, 235s timeout). NOT related to merge — unchanged Supabase
  test infra times out without live network. Flagged in PR body.

Token-ceiling warnings on plan-ceo-review (29K), office-hours (26K),
and ship (34K). These existed on origin/main before the merge — the
preamble grew substantially from main's GBrain + UX additions plus this
branch's continuous-checkpoint, context-health, model-overlay, taste-profile,
and feature-discovery additions. Worth a follow-up reduction pass but
doesn't block this merge.

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

bin/gstack-settings-hook

@@ -54,7 +54,7 @@ case "$ACTION" in
     " 2>/dev/null
     ;;
   remove)
-    [ -f "$SETTINGS_FILE" ] || exit 0
+    [ -f "$SETTINGS_FILE" ] || exit 1
     GSTACK_SETTINGS_PATH="$SETTINGS_FILE" bun -e "
       const fs = require('fs');
       const settingsPath = process.env.GSTACK_SETTINGS_PATH;