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>

qa/SKILL.md

@@ -137,6 +137,26 @@ AI-assisted coding makes the marginal cost of completeness near-zero. When you p
 - BAD: "Let's defer test coverage to a follow-up PR." (Tests are the cheapest lake to boil.)
 - BAD: Quoting only human-team effort: "This would take 2 weeks." (Say: "2 weeks human / ~1 hour CC.")
 
+## Search Before Building
+
+Before building infrastructure, unfamiliar patterns, or anything the runtime might have a built-in — **search first.** Read `~/.claude/skills/gstack/ETHOS.md` for the full philosophy.
+
+**Three layers of knowledge:**
+- **Layer 1** (tried and true — in distribution). Don't reinvent the wheel. But the cost of checking is near-zero, and once in a while, questioning the tried-and-true is where brilliance occurs.
+- **Layer 2** (new and popular — search for these). But scrutinize: humans are subject to mania. Search results are inputs to your thinking, not answers.
+- **Layer 3** (first principles — prize these above all). Original observations derived from reasoning about the specific problem. The most valuable of all.
+
+**Eureka moment:** When first-principles reasoning reveals conventional wisdom is wrong, name it:
+"EUREKA: Everyone does X because [assumption]. But [evidence] shows this is wrong. Y is better because [reasoning]."
+
+Log eureka moments:
+```bash
+jq -n --arg ts "$(date -u +%Y-%m-%dT%H:%M:%SZ)" --arg skill "SKILL_NAME" --arg branch "$(git branch --show-current 2>/dev/null)" --arg insight "ONE_LINE_SUMMARY" '{ts:$ts,skill:$skill,branch:$branch,insight:$insight}' >> ~/.gstack/analytics/eureka.jsonl 2>/dev/null || true
+```
+Replace SKILL_NAME and ONE_LINE_SUMMARY. Runs inline — don't stop the workflow.
+
+**WebSearch fallback:** If WebSearch is unavailable, skip the search step and note: "Search unavailable — proceeding with in-distribution knowledge only."
+
 ## Contributor Mode
 
 If `_CONTRIB` is `true`: you are in **contributor mode**. You're a gstack user who also helps make it better.