Fix subagent announce failover race (always emit lifecycle end + treat timeout=0 as no-timeout) (#6621)

* Fix subagent announce race and timeout handling

Bug 1: Subagent announce fires before model failover retries finish
- Problem: CLI provider emitted lifecycle error on each attempt, causing
  subagent registry to prematurely call beginSubagentCleanup() and announce
  with incorrect status before failover retries completed
- Fix: Removed lifecycle error emission from CLI provider's attempt-level
  .catch() in agent-runner-execution.ts. Errors still propagate to
  runWithModelFallback for retry, but no intermediate lifecycle events
  are emitted. Only the final outcome (after all retries) emits lifecycle
  events.

Bug 2: Hard 600s per-prompt timeout ignores runTimeoutSeconds=0
- Problem: When runTimeoutSeconds=0 (meaning 'no timeout'), the code
  returned the default 600s timeout instead of respecting the 0 setting
- Fix: Modified resolveAgentTimeoutMs() to treat 0 as 'no timeout' and
  return a very large timeout value (30 days) instead of the default.
  This avoids setTimeout issues with Infinity while effectively providing
  unlimited time for long-running tasks.

* fix: emit lifecycle:error for CLI failures (#6621) (thanks @tyler6204)

* chore: satisfy format/lint gates (#6621) (thanks @tyler6204)

* fix: restore build after upstream type changes (#6621) (thanks @tyler6204)

* test: fix createSystemPromptOverride tests to match new return type (#6621) (thanks @tyler6204)

src/agents/pi-embedded-runner.createsystempromptoverride.test.ts

@@ -99,12 +99,12 @@ const _readSessionMessages = async (sessionFile: string) => {
 };
 
 describe("createSystemPromptOverride", () => {
-  it("returns the override prompt regardless of default prompt", () => {
+  it("returns the override prompt trimmed", () => {
     const override = createSystemPromptOverride("OVERRIDE");
-    expect(override("DEFAULT")).toBe("OVERRIDE");
+    expect(override).toBe("OVERRIDE");
   });
   it("returns an empty string for blank overrides", () => {
     const override = createSystemPromptOverride("  \n  ");
-    expect(override("DEFAULT")).toBe("");
+    expect(override).toBe("");
   });
 });