Fail fast and clean up when Playground bind port is occupied

[chubes4]

Problem

A recipe-run selected a loopback port already held by an existing SSH listener. Playground emitted listen EADDRINUSE, but the run remained blocked in input.materialize until the outer 20-minute timeout sent SIGTERM. The managed disposable MySQL container remained running and required operator cleanup.

Evidence

• Bind error: listen EADDRINUSE: address already in use 127.0.0.1:63055.
• The pre-existing owner was an SSH listener with PPID 1, started roughly 14 hours before the recipe run.
• Artifact pointer remained at lastCommand: input.materialize and recorded interruption by SIGTERM only when the outer timeout expired.
• The managed wp-codebox-mysql-* container remained up after termination.

Expected

1. Dynamic Playground port allocation excludes ports that cannot be bound, or retries allocation on EADDRINUSE.
2. Runtime startup/materialization propagates the bind failure immediately instead of hanging.
3. Managed runtime services are torn down on this terminal startup failure and SIGTERM path.

Reproduction

1. Hold a local TCP listener on a candidate Playground bind port.
2. Force or stub dynamic allocation to return that occupied port.
3. Run a recipe with a managed service and an input mount requiring materialization.
4. Assert the run fails promptly with structured bind diagnostics and the managed service lifecycle reaches released/teardown: completed.

Discovered while validating #1821 against a real mounted WPCOM PHPUnit recipe.

[chubes4]

Confirmed independently through the current Homeboy WordPress PHPUnit path against a generated WPCOM runtime. Playground emitted listen EADDRINUSE ... 127.0.0.1:63249 immediately after runtime startup, but the run stayed in input.materialize for 1,500,065 ms before recipe-run-timeout. Failure recovery then spent another 30 seconds collecting artifacts and reported none. No PHPUnit execution occurred. This demonstrates the hang affects the standard wordpress.phpunit recipe path and turns an immediate bind error into a 25-minute false materialization timeout.