Execute bounded plans through one recipe runtime

[chubes4]

Summary

Execute a generic bounded command plan through one prepared WP Codebox recipe workspace, runtime, and service lifecycle.

What changed

• Add the public executeBoundedRecipePlan() Node API and wp-codebox.bounded-runtime-plan recipe command.
• Give each entry isolated environment, process identity, artifact namespace, timeout signal, outputs, duration, and stable result ordering.
• Make concurrent Playground commands use execution-local abort signals and namespaced PHPUnit diagnostics.
• Derive runtime policy from nested plan commands and redact persisted bounded-plan arguments.
• Upgrade the disposable MariaDB integration to run two real PHPUnit processes against one shared service with distinct database indexes.

How to test

1. Run npm ci; expect dependencies to install successfully.
2. Run npm run build; expect all TypeScript packages to build.
3. Run npm run test:bounded-runtime-plan; expect scheduler, timeout, fail-fast, and lifecycle assertions to pass.
4. Run npm run test:bounded-recipe-plan; expect public recipe-plan adapter assertions to pass.
5. Run npm run test:bounded-recipe-plan-integration; expect two commands to execute through one real Playground lifecycle.
6. Run npm run test:public-api-contract; expect the documented package exports and command contract to pass.
7. On a Docker-capable host, run npm run test:disposable-mysql-mysqli-e2e; expect two real PHPUnit processes to share one MariaDB service while using distinct TC_DB_INDEX values.

Compatibility

Additive API and recipe-command surface. Existing single-recipe behavior and extension paths are unchanged.

Evidence

• Local build and deterministic tests above pass.
• The Docker test is required in Agent Task Contracts CI because Docker is unavailable on the development host.
• Owning issue and full acceptance contract: Execute bounded plans through one workspace recipe lifecycle #1923
• Downstream tracker: https://linear.app/a8c/issue/BET-12/local-wordpresscom-development-with-wpcom-codebox

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode
• Model: openai/gpt-5.6-sol
• Used for: Implemented and tested the change; Chris reviews and owns it.

Closes #1923