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>

scripts/gen-skill-docs.ts

@@ -263,6 +263,28 @@ AI-assisted coding makes the marginal cost of completeness near-zero. When you p
 - BAD: Quoting only human-team effort: "This would take 2 weeks." (Say: "2 weeks human / ~1 hour CC.")`;
 }
 
+function generateSearchBeforeBuildingSection(ctx: TemplateContext): string {
+  return `## Search Before Building
+
+Before building infrastructure, unfamiliar patterns, or anything the runtime might have a built-in — **search first.** Read \`${ctx.paths.skillRoot}/ETHOS.md\` for the full philosophy.
+
+**Three layers of knowledge:**
+- **Layer 1** (tried and true — in distribution). Don't reinvent the wheel. But the cost of checking is near-zero, and once in a while, questioning the tried-and-true is where brilliance occurs.
+- **Layer 2** (new and popular — search for these). But scrutinize: humans are subject to mania. Search results are inputs to your thinking, not answers.
+- **Layer 3** (first principles — prize these above all). Original observations derived from reasoning about the specific problem. The most valuable of all.
+
+**Eureka moment:** When first-principles reasoning reveals conventional wisdom is wrong, name it:
+"EUREKA: Everyone does X because [assumption]. But [evidence] shows this is wrong. Y is better because [reasoning]."
+
+Log eureka moments:
+\`\`\`bash
+jq -n --arg ts "$(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."`;
+}
+
 function generateContributorMode(): string {
   return `## Contributor Mode
 
@@ -365,6 +387,7 @@ function generatePreamble(ctx: TemplateContext): string {
     generateTelemetryPrompt(ctx),
     generateAskUserFormat(ctx),
     generateCompletenessSection(),
+    generateSearchBeforeBuildingSection(ctx),
     generateContributorMode(),
     generateCompletionStatus(),
   ].join('\n\n');