Fix watcher shutdown lifecycle

[Way-To-AGI]

What changed

• enforce one Theme Studio watcher per CDP port with an atomic private lock
• reconcile and stop only exact validated watcher commands, including orphaned duplicates
• make signal, API, and renderer-disappearance shutdown release sessions, control server, state, and lock deterministically
• prune closed CDP sessions during theme switches
• add lifecycle regression coverage and update runtime/QA documentation

Root cause

Restore deleted the single watcher state shortly after SIGTERM without confirming process exit. Older detached watchers became undiscoverable, so repeated starts accumulated CDP and loopback connections that could interfere with Codex graceful quit.

Validation

• node scripts/self-test.mjs
• node scripts/studio-protocol-test.mjs
• node scripts/theme-control-test.mjs
• node scripts/usage-provider-test.mjs
• node scripts/platform-runtime-test.mjs
• node scripts/runtime-lifecycle-test.mjs
• quick_validate.py
• cleaned three existing orphan watchers and verified state/lock removal

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