Fix Modal cleanup after app settings change

[ymichael]

Human comments

What was wrong

After Modal creates a sandbox but saving its resource checkpoint fails, cleanup has only the allocation key. Reconciliation looked in the currently configured app, so changing App Name could make cleanup report success while leaving the original sandbox running. This affects the cleanup path introduced in #3274.

What changed

Find sandboxes across apps in the current Modal environment using the existing bbMachineKey tag, terminate every match, and verify removal by sandbox ID. Enumeration and termination failures remain retryable. The change stays inside the Modal plugin and requires no new stored fields, migration, core changes, or protocol changes.

How you verified

• The cross-app regression failed before the fix and passes afterward. Tests cover duplicate matching allocations, unrelated sandboxes, repeated cleanup, and enumeration/termination failures followed by retry.
• pnpm exec turbo run test typecheck prepare:bundled lint --filter=bb-plugin-environment-modal-sandbox passed, including 52 tests.
• A local probe exercised the actual cleanup route with migrated SQLite and an injected checkpoint failure. An installed-SDK probe verified tag filtering without an app filter and pagination. Both used simulated external compute; no live Modal API calls were made.

AGENT GENERATED