Block conflicting site operations

[bcotrim]

Related issues

• STU-2220

How AI was used in this PR

Claude Code handled the implementation. I designed the solution, reviewed and iterated over the code, and manually tested.

Proposed Changes

Two Studio operations on the same site could run at once and corrupt each other. Starting a site while it was stopping left it down while the UI claimed it started, then looped retrying. Because the agent calls the CLI directly, guarding this in the UI alone wouldn't hold.

The CLI now claims a per-site lease for each operation and refuses a conflicting one with a readable error — so the guard applies no matter who started the work: you, the agent, a terminal, or a second window. Operations that restart the site or rewrite its files (start, stop, delete, import, pull, settings) run alone; read-only ones (export, push) run alongside each other.

The lease reaches the UI, which disables the actions it blocks and names what's running ("Exporting…") rather than leaving controls that look live but swallow the click. Progress survives navigating away and back, and a lease whose owning process dies is reclaimed automatically, so a crash can't wedge a site.

Testing Instructions

1. Start a long export: studio export --path <site> <out.tar.gz>.
2. While it runs, try to start / delete / change settings on that site — from the sidebar, the site dropdown and the overview screen, and by asking the agent. Controls are disabled and read "Exporting…"; the agent gets a readable refusal.
3. Navigate away from the site and back — it still shows as exporting.
4. Let it finish — everything re-enables.
5. Repeat, but kill -9 the export mid-run. The site must not stay locked.

Verified in light and dark mode.

Pre-merge Checklist

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

🤖 Generated with Claude Code

[wpmobilebot]

📊 Performance Test Results

Comparing a57383e vs trunk

app-size

Metric	trunk	a57383e	Diff	Change
App Size (Mac)	1372.96 MB	1372.96 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	a57383e	Diff	Change
load	1064 ms	1038 ms	26 ms	⚪ 0.0%

site-startup

Metric	trunk	a57383e	Diff	Change
siteCreation	6527 ms	6507 ms	20 ms	⚪ 0.0%
siteStartup	2381 ms	2358 ms	23 ms	⚪ 0.0%

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Results are median values from multiple test runs.

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