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>

CLAUDE.md

@@ -78,6 +78,7 @@ gstack/
 ├── setup            # One-time setup: build binary + symlink skills
 ├── SKILL.md         # Generated from SKILL.md.tmpl (don't edit directly)
 ├── SKILL.md.tmpl    # Template: edit this, run gen:skill-docs
+├── ETHOS.md         # Builder philosophy (Boil the Lake, Search Before Building)
 └── package.json     # Build scripts for browse
 ```
 
@@ -192,6 +193,19 @@ Completeness is cheap. Don't recommend shortcuts when the complete implementatio
 is a "lake" (achievable) not an "ocean" (multi-quarter migration). See the
 Completeness Principle in the skill preamble for the full philosophy.
 
+## Search before building
+
+Before designing any solution that involves concurrency, unfamiliar patterns,
+infrastructure, or anything where the runtime/framework might have a built-in:
+
+1. Search for "{runtime} {thing} built-in"
+2. Search for "{thing} best practice {current year}"
+3. Check official runtime/framework docs
+
+Three layers of knowledge: tried-and-true (Layer 1), new-and-popular (Layer 2),
+first-principles (Layer 3). Prize Layer 3 above all. See ETHOS.md for the full
+builder philosophy.
+
 ## Local plans
 
 Contributors can store long-range vision docs and design documents in `~/.gstack-dev/plans/`.