Phase 2: analysis layer (analyze.js), cache guard, log hygiene

- analyze.js: burn rate, weekly reconstruction, cycle stagger, rotation
  rank, underspend alerts, log prune with weekly archive
- logger.js: getCachedRun(maxAgeMinutes) — skip probing if recent data exists
- monitor.js: cache guard at wake — 20-min dedup, zero extra API calls
- test.js: fix type assertion for gemini-api/xai-api providers (+5 passing);
  add 14 new tests for cache guard and analyze.js (162 total, all green)
- docs/analyze.md: usage reference

Co-authored-by: Hannibal Smith <hannibal@trentuna.com>

monitor.js

@@ -58,6 +58,20 @@ async function probeProvider(p) {
 }
 
 async function main() {
+  // Cache guard — return last logged run if within 20 minutes (skip on --summary, --no-log, --provider filter)
+  if (!noLog && !filterProvider && !isSummaryOnly) {
+    const { getCachedRun } = await import('./logger.js');
+    const cached = getCachedRun(20);
+    if (cached) {
+      if (isJson) {
+        console.log(JSON.stringify(cached, null, 2));
+      } else {
+        console.log(generateReport(cached));
+      }
+      return;
+    }
+  }
+
   const allProviders = getProviders();
   const providerNames = filterProvider
     ? [filterProvider]