Resume parked work when a provider's monthly limit is raised

The heartbeat scheduler enqueued runs even while a provider's monthly
usage window was full, so every task burned its 3-attempt retry budget
on instant quota failures within seconds and stayed dead forever -
raising the limit (or restarting) never revived anything.

- Park tasks (skip enqueue) while their provider is at its
  monthly_request_limit instead of creating runs doomed to fail
- Exclude quota-blocked failures from the 3-attempt retry budget,
  retroactively reviving tasks abandoned by past filled windows
- Share the gate message as PROVIDER_MONTHLY_LIMIT_MESSAGE and log
  quota-block transitions once per state change for diagnosability
- Ignore landing/ (self-contained Next.js sub-project) and
  built-in skills/ (prompt content) in eslint so verify:ci lints only
  application code

src/shared/provider-runtime-domain.ts

@@ -29,6 +29,15 @@ export interface ProviderRateLimitObservationRecord extends ProviderObservedRate
   observedAt: string;
 }
 
+/**
+ * Exact message recorded on runs blocked by a provider's monthly usage window.
+ * The heartbeat scheduler matches task_runs.error_message against this string
+ * so quota-blocked attempts never consume a task's retry budget — the text is
+ * a cross-module contract and also matches rows written by earlier builds
+ * that inlined it.
+ */
+export const PROVIDER_MONTHLY_LIMIT_MESSAGE = "Provider monthly request limit has been reached.";
+
 export function currentProviderUsageWindow(now = new Date()): { start: string; end: string } {
   const start = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), 1));
   const end = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth() + 1, 1));