Fix bindSession ConflictException crashing control-plane

[ajit-zer07]

Summary

• Harden RunManagerService.bindSession against races where the run has
  already advanced past binding_session (e.g., SessionDiscoveryService
  and RunExecutorService both processing the same session). The method
  now catches ConflictException from transitionTo, logs a warning, and
  returns the current run — avoiding duplicate event emission and session
  upserts.
• Stop SessionDiscoveryService.handleSessionCreated from firing three
  unawaited void state transitions. They are now awaited sequentially
  inside a try/catch, so a transition failure on one discovered session
  no longer kills the WatchSessions loop for every other session.

Why

Previously, void this.runManager.bindSession(...) in
session-discovery.service.ts:98 would surface any ConflictException
from the state-machine guard (run.repository.ts:102) as an unhandled
promise rejection — crashing the control-plane. This was observed from
the UIConsole as a control-plane crash during session binding.

Root cause:

1. transitionTo throws ConflictException when the current status is
   not a valid predecessor for the target (e.g., run already running).
2. Three void calls (markStarted, bindSession, markRunning) run
   concurrently and out of order relative to the state machine.
3. Unhandled rejection → process exit.

Changes

• src/runs/run-manager.service.ts
  • Import ConflictException from @nestjs/common.
  • In bindSession, wrap markBindingSession in try/catch. On
    ConflictException, fetch the current run, log a warning with the
    current status, and return it. Throws NotFoundException only if the
    run genuinely disappeared.
• src/runs/session-discovery.service.ts
  • Replace the three void state transitions with sequential awaits
    inside a try/catch.
  • Errors are logged but swallowed so subsequent subscribeSession +
    streamConsumer.start still execute — observation is the whole
    point of session discovery — and the outer WatchSessions loop
    stays alive for other sessions.

Test plan

• npx tsc --noEmit -p tsconfig.json — clean.
• npx jest src/runs/run-manager.service.spec.ts — 19 / 19 pass.
• npx jest src/runs/session-discovery.service.spec.ts — 9 / 9 pass.
• npx jest src/runs/run-executor.service.spec.ts — 24 / 24 pass.
• npx jest (full suite) — 593 / 593 pass across 46 suites.
• Manual: run control-plane against runtime, trigger a session twice
  (RunExecutor + SessionDiscovery on the same sessionId), confirm no
  crash and a single session.bound event is emitted.

Out of scope / follow-ups

• markStarted and markRunning still throw ConflictException on
  racing callers. They are now caught by the new try/catch in
  session-discovery.service.ts, but could be made idempotent in
  RunManagerService for consistency with markCompleted /
  markFailed / markCancelled.
• void this.streamConsumer.start(...) in handleSessionCreated is
  still unawaited; it's long-running by design, but a .catch handler
  would make rejections observable rather than unhandled.