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>

plan-ceo-review/SKILL.md

@@ -17,6 +17,7 @@ allowed-tools:
   - Glob
   - Bash
   - AskUserQuestion
+  - WebSearch
 ---
 <!-- AUTO-GENERATED from SKILL.md.tmpl — do not edit directly -->
 <!-- Regenerate: bun run gen:skill-docs -->
@@ -405,6 +406,22 @@ Analyze the plan. If it involves ANY of: new UI screens/pages, changes to existi
 Identify 2-3 files or patterns in the existing codebase that are particularly well-designed. Note them as style references for the review. Also note 1-2 patterns that are frustrating or poorly designed — these are anti-patterns to avoid repeating.
 Report findings before proceeding to Step 0.
 
+### Landscape Check
+
+Read ETHOS.md for the Search Before Building framework (the preamble's Search Before Building section has the path). Before challenging scope, understand the landscape. WebSearch for:
+- "[product category] landscape {current year}"
+- "[key feature] alternatives"
+- "why [incumbent/conventional approach] [succeeds/fails]"
+
+If WebSearch is unavailable, skip this check and note: "Search unavailable — proceeding with in-distribution knowledge only."
+
+Run the three-layer synthesis:
+- **[Layer 1]** What's the tried-and-true approach in this space?
+- **[Layer 2]** What are the search results saying?
+- **[Layer 3]** First-principles reasoning — where might the conventional wisdom be wrong?
+
+Feed into the Premise Challenge (0A) and Dream State Mapping (0C). If you find a eureka moment, surface it during the Expansion opt-in ceremony as a differentiation opportunity. Log it (see preamble).
+
 ## Step 0: Nuclear Scope Challenge + Mode Selection
 
 ### 0A. Premise Challenge

plan-ceo-review/SKILL.md.tmpl

@@ -17,6 +17,7 @@ allowed-tools:
   - Glob
   - Bash
   - AskUserQuestion
+  - WebSearch
 ---
 
 {{PREAMBLE}}
@@ -147,6 +148,22 @@ Analyze the plan. If it involves ANY of: new UI screens/pages, changes to existi
 Identify 2-3 files or patterns in the existing codebase that are particularly well-designed. Note them as style references for the review. Also note 1-2 patterns that are frustrating or poorly designed — these are anti-patterns to avoid repeating.
 Report findings before proceeding to Step 0.
 
+### Landscape Check
+
+Read ETHOS.md for the Search Before Building framework (the preamble's Search Before Building section has the path). Before challenging scope, understand the landscape. WebSearch for:
+- "[product category] landscape {current year}"
+- "[key feature] alternatives"
+- "why [incumbent/conventional approach] [succeeds/fails]"
+
+If WebSearch is unavailable, skip this check and note: "Search unavailable — proceeding with in-distribution knowledge only."
+
+Run the three-layer synthesis:
+- **[Layer 1]** What's the tried-and-true approach in this space?
+- **[Layer 2]** What are the search results saying?
+- **[Layer 3]** First-principles reasoning — where might the conventional wisdom be wrong?
+
+Feed into the Premise Challenge (0A) and Dream State Mapping (0C). If you find a eureka moment, surface it during the Expansion opt-in ceremony as a differentiation opportunity. Log it (see preamble).
+
 ## Step 0: Nuclear Scope Challenge + Mode Selection
 
 ### 0A. Premise Challenge