feat: Search Before Building — builder ethos + skill integrations (v0.9.5.0) (#298)

* feat: ETHOS.md — gstack builder philosophy

Standalone document capturing the four principles: The Golden Age,
Boil the Lake, Search Before Building, and Build for Yourself.

Introduces the three-layer knowledge framework (tried-and-true,
new-and-popular, first-principles) and the Eureka Moment concept —
when first-principles reasoning reveals conventional wisdom is wrong.

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

* feat: Search Before Building preamble section + CLAUDE.md

Add generateSearchBeforeBuildingSection(ctx) to gen-skill-docs.ts.
Every workflow skill now gets a compact router section covering:
- Three layers of knowledge (tried-and-true, new-and-popular, first-principles)
- Eureka moment format and jq-based JSONL logging
- WebSearch fallback clause
- ETHOS.md reference via ctx.paths.skillRoot resolver

Also adds compact "Search before building" section to CLAUDE.md.

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

* feat: skill-specific Search Before Building integrations

8 template changes:
- /office-hours: Phase 2.75 Landscape Awareness (WebSearch + three-layer synthesis)
- /plan-eng-review: Step 0 search check with layer provenance annotations
- /investigate: external pattern search + search escalation on hypothesis failure
- /plan-ceo-review: Landscape Check before scope challenge
- /review: search-before-recommending for fix patterns
- /qa-only: WebSearch in allowed-tools
- /design-consultation: three-layer synthesis backport in Phase 2 Step 3
- /retro: eureka moment tracking from ~/.gstack/analytics/eureka.jsonl

All search steps include WebSearch fallback clause.

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

* feat: v0.9.5.0 — Builder Ethos (CHANGELOG + VERSION + TODOS)

ETHOS.md + Search Before Building across all workflow skills.
Deferred: first-time intro flow (blocked on blog post).

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

* fix: address Codex review — sanitize search, privacy gate, ETHOS.md sidecar

Three fixes from adversarial Codex review:
- /investigate: sanitize error messages before searching (strip hostnames,
  IPs, file paths, SQL, customer data). Skip search if unsanitizable.
- /office-hours: add privacy gate before landscape search. Use generalized
  category terms, never the user's specific product name or stealth idea.
- setup: link ETHOS.md into .agents/skills/gstack/ sidecar so workspace-
  local Codex sessions can find the builder philosophy.

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

* fix: sanitize Phase 2 external pattern search in /investigate

The Phase 2 external search also sent raw error messages to WebSearch.
Apply same sanitization rule as Phase 3 search escalation.

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

* docs: sync documentation with shipped changes

- ARCHITECTURE.md: preamble now handles 5 things (add Search Before Building)
- CLAUDE.md: add ETHOS.md to project structure tree
- README.md: add ETHOS.md to docs table

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

---------

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

ARCHITECTURE.md

@@ -210,12 +210,13 @@ This is structurally sound — if a command exists in code, it appears in docs.
 
 ### The preamble
 
-Every skill starts with a `{{PREAMBLE}}` block that runs before the skill's own logic. It handles four things in a single bash command:
+Every skill starts with a `{{PREAMBLE}}` block that runs before the skill's own logic. It handles five things in a single bash command:
 
 1. **Update check** — calls `gstack-update-check`, reports if an upgrade is available.
 2. **Session tracking** — touches `~/.gstack/sessions/$PPID` and counts active sessions (files modified in the last 2 hours). When 3+ sessions are running, all skills enter "ELI16 mode" — every question re-grounds the user on context because they're juggling windows.
 3. **Contributor mode** — reads `gstack_contributor` from config. When true, the agent files casual field reports to `~/.gstack/contributor-logs/` when gstack itself misbehaves.
 4. **AskUserQuestion format** — universal format: context, question, `RECOMMENDATION: Choose X because ___`, lettered options. Consistent across all skills.
+5. **Search Before Building** — before building infrastructure or unfamiliar patterns, search first. Three layers of knowledge: tried-and-true (Layer 1), new-and-popular (Layer 2), first-principles (Layer 3). When first-principles reasoning reveals conventional wisdom is wrong, the agent names the "eureka moment" and logs it. See `ETHOS.md` for the full builder philosophy.
 
 ### Why committed, not generated at runtime?