Serialize live integration test files

[alex-w-99]

Executive Summary

Run live integration test files sequentially to prevent overlapping checks against the same agent.

• Apply the scheduling policy to both CI and local live-suite invocations.
• Bump the plugin to 0.2.12, synchronize the lockfile version, and update the changelog.

Description

Set fileParallelism: false in vitest.live.config.ts. The email and SMS test files use shared agent fixtures, so running one file at a time prevents their requests and cleanup hooks from overlapping.

Reason

Concurrent channel checks can interfere with each other when they share an agent session. Serial execution lets each file finish its reply checks and cleanup before the next begins.

Decisions

• Scheduling: Put serialization in the shared live-suite configuration so CI and local invocations follow the same execution policy.

Testing

• npm test: all 891 tests passed across 74 files.
• npm run lint, npm run typecheck, and npm run build: passed.
• uv run --no-project python -m unittest tests/live/test_a2a_preflight.py: all four tests passed.
• Loaded the live configuration through Vitest's API and asserted fileParallelism === false and maxWorkers === 1; both checks passed.
• Ran npx vitest run --config vitest.live.config.ts tests/live/email-reply.test.ts tests/live/sms.test.ts with both live credentials unset: both files loaded and all four live tests skipped as expected. Actual email/SMS delivery was not exercised locally.

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