Studio Code: Close daemon socket after per-turn site status check so headless runs can exit

[shaunandrews]

Related issues

• Fixes STU-2040
• Related to STU-2001 / Resolve the real site running state when resuming code sessions headlessly #4096

How AI was used in this PR

Claude Code applied the fix, verified it end-to-end in both directions (fixed build exits, unfixed build hangs), and drafted this PR. I reviewed and directed the work.

Proposed Changes

Since #4096, every headless studio code … --json turn on a local site leaves the CLI process alive after it reports turn.completed. The per-turn site running-state check opens a connection to the process-manager daemon and never closes it, and that open socket keeps the process from exiting.

The desktop app feels this the most: each turn forks a headless code sessions resume child and treats the child's exit as the end of the turn. Because the child never exits, the session appears stuck in the working state forever — the stop button and the sidebar agent-activity indicator never clear — and an orphaned node process piles up for every turn taken on a running-or-stopped local site.

The fix closes the daemon connection as soon as the running-state check completes, the same way every other daemon consumer in the CLI already does. The connection is a singleton, so anything later in the turn that needs the daemon (like the WP-CLI tool) reconnects transparently.

Testing Instructions

1. npm run cli:build
2. Run a headless turn against a local site: node apps/cli/dist/cli/main.mjs code --json --path ~/Studio/<site> "Reply with only the word OK."
3. The process should exit on its own a moment after the turn.completed event (on trunk it hangs indefinitely and must be killed).
4. In the desktop app, take a turn in a Studio Code session on a local site and confirm the working indicator clears when the turn finishes.
5. Tests: npm test -- apps/cli/commands/ai/sessions/tests/resume.test.ts apps/cli/commands/ai/tests/index.test.ts

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

🤖 Generated with Claude Code

[wpmobilebot]

📊 Performance Test Results

Comparing 46a8dd0 vs trunk

app-size

Metric	trunk	46a8dd0	Diff	Change
App Size (Mac)	1419.35 MB	1419.35 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	46a8dd0	Diff	Change
load	1067 ms	1032 ms	35 ms	⚪ 0.0%

site-startup

Metric	trunk	46a8dd0	Diff	Change
siteCreation	6961 ms	6973 ms	+12 ms	⚪ 0.0%
siteStartup	2383 ms	2387 ms	+4 ms	⚪ 0.0%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)

[bcotrim]

LGTM 👍