merge(dev): resolve background-agent delegated fallback conflicts

Reconcile the latest dev branch changes with the delegated child-session fallback work. Preserve the upstream background-agent updates while keeping the delegated bootstrap cleanup and compatibility wiring fixes intact, then re-verify the affected regression suites and typecheck.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/runtime-fallback/AGENTS.md

@@ -1,6 +1,6 @@
 # src/hooks/runtime-fallback/ — Reactive Provider Error Recovery
 
-**Generated:** 2026-04-11
+**Generated:** 2026-05-08
 
 ## OVERVIEW
 

src/hooks/runtime-fallback/error-classifier.ts

@@ -132,7 +132,8 @@ export function classifyErrorType(error: unknown): string | undefined {
     /exhausted\s+your\s+capacity/i.test(message) ||
     /out\s+of\s+credits?/i.test(message) ||
     /payment.?required/i.test(message) ||
-    /usage\s+limit/i.test(message)
+    /usage\s+limit/i.test(message) ||
+    /credit\s+balance.*too\s+low/i.test(message)
   ) {
     return "quota_exceeded"
   }

src/hooks/runtime-fallback/fallback-state.ts

@@ -28,6 +28,10 @@ export function findNextAvailableFallback(
 ): string | undefined {
   for (let i = state.fallbackIndex + 1; i < fallbackModels.length; i++) {
     const candidate = fallbackModels[i]
+    if (candidate === state.currentModel) {
+      log(`[${HOOK_NAME}] Skipping fallback model (same as current)`, { model: candidate, index: i })
+      continue
+    }
     if (!isModelInCooldown(candidate, state, cooldownSeconds)) {
       return candidate
     }