[P2] Make the proposed compiled host launcher atomic and dependency-aware #272

From the September 28, 2026 worker assessment. Sean authorized implementing these follow-ups.

Static review of PR #244 found concurrent launchers can compile into the same output directory without locking/staging, and its build fingerprint omits the lockfile/compiler identity.

Source: scripts/run-compiled.mjs.

Acceptance criteria:

• Build on PR feat: precompile host scripts, run one plain node process per service (SYD-268) #244 without duplicating or merging its existing work.
• Isolate competing builds and publish only complete output atomically; running services must retain a stable generation for later imports.
• Include dependency/compiler changes in freshness checks and test concurrent startup and failed compilation behavior.

Preserve human-only merge/triage decisions and existing claim/lease authorization. No deployment is part of this issue.