fix: speed up handbook sync and stop llm_calls 404 noise

Handbook sync ran files sequentially under a 5 req/min limiter with a
hardcoded 60s LLM timeout, causing long syncs and AbortError timeouts on
large files. Now: limiter at 20 req/min, files processed with concurrency
4, handbook extraction timeout raised to 180s, and near-empty files skip
the LLM call.

callLLM gains a timeoutMs option; passing a signal no longer silently
disables the per-request timeout.

llm_calls telemetry self-disables after the first 404 so deploys without
the migration applied don't spam the console.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/extractionPipeline.js

@@ -67,6 +67,7 @@ export async function analyzeHandbookDelta(fileContent, filePath, { signal } = {
     tools: [EMIT_HANDBOOK_DELTA_TOOL],
     toolChoice: { type: 'tool', name: EMIT_HANDBOOK_DELTA_TOOL.name },
     maxTokens: 8192,
+    timeoutMs: 180_000,
     limiter: extractionLimiter,
     signal,
   });