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>

CHANGELOG.md

@@ -1,9 +1,16 @@
 # Changelog
 
-## [0.9.5.0] - 2026-03-21 — CEO Review ↔ Office Hours Chaining
+## [0.9.5.0] - 2026-03-21 — Builder Ethos
 
 ### Added
 
+- **ETHOS.md — gstack's builder philosophy in one document.** Four principles: The Golden Age (AI compression ratios), Boil the Lake (completeness is cheap), Search Before Building (three layers of knowledge), and Build for Yourself. This is the philosophical source of truth that every workflow skill references.
+- **Every workflow skill now searches before recommending.** Before suggesting infrastructure patterns, concurrency approaches, or framework-specific solutions, gstack checks if the runtime has a built-in and whether the pattern is current best practice. Three layers of knowledge — tried-and-true (Layer 1), new-and-popular (Layer 2), and first-principles (Layer 3) — with the most valuable insights prized above all.
+- **Eureka moments.** When first-principles reasoning reveals that conventional wisdom is wrong, gstack names it, celebrates it, and logs it. Your weekly `/retro` now surfaces these insights so you can see where your projects zigged while others zagged.
+- **`/office-hours` adds Landscape Awareness phase.** After understanding your problem through questioning but before challenging premises, gstack searches for what the world thinks — then runs a three-layer synthesis to find where conventional wisdom might be wrong for your specific case.
+- **`/plan-eng-review` adds search check.** Step 0 now verifies architectural patterns against current best practices and flags custom solutions where built-ins exist.
+- **`/investigate` searches on hypothesis failure.** When your first debugging hypothesis is wrong, gstack searches for the exact error message and known framework issues before guessing again.
+- **`/design-consultation` three-layer synthesis.** Competitive research now uses the structured Layer 1/2/3 framework to find where your product should deliberately break from category norms.
 - **CEO review saves context when handing off to `/office-hours`.** When `/plan-ceo-review` suggests running `/office-hours` first, it now saves a handoff note with your system audit findings and any discussion so far. When you come back and re-invoke `/plan-ceo-review`, it picks up that context automatically — no more starting from scratch.
 
 ## [0.9.4.1] - 2026-03-20