feat(docker): parallel test runs across git worktrees without port conflicts (closes #676)

[s2x]

Description

Closes #676

Changes

• bin/docker-test-worktree (new): runs composer test/test:coverage/lint for any git worktree in its own container of the workerman-bundle-test image. Each container has its own network namespace, so N parallel worktree suites cannot collide on ports 8888/9999/9991 — no -p, no code change. Container name (wmb-<worktree-basename>) and vendor volume (wmb-vendor-<worktree-basename>) are unique per checkout; var/ stays in the worktree's own bind mount. --publish starts ONLY the daemon with ephemeral host mappings (-p 127.0.0.1::8888|9999|9991), waits for all three ports to accept in-container, prints the mappings, and blocks until Ctrl-C/TERM (trap removes the container). Readiness failure is loud: prints a docker logs --tail 20 excerpt and removes the container.
• tests/App/Kernel.php: the three listen addresses honour WMB_LISTEN_ADDR (default 127.0.0.1 — unset behavior is byte-identical), required for the publish flow so forwarded host connections reach the bridge interface.
• CONTRIBUTING.md: new "Parallel test runs across git worktrees" subsection (network-namespace guarantee, never-share-var/ rule, per-worktree vendor volumes, publish/curl debug flow); the outdated ports note now lists all three ports and documents WMB_LISTEN_ADDR.
• Cross-environment cache poisoning guard: the helper purges var/cache/dev/workerman/config.cache.php* at startup — a cache written inside the container holds /app-prefixed paths that crash host runs with mkdir(): Read-only file system, and vice versa a host-written cache trips the container-side ownership guard.

Changelog

Two entries under \[Unreleased\] → Added (helper + docs; WMB_LISTEN_ADDR).

Proof of Work

docs/proof_of_work/0676-docker-worktree-parallel-tests/ — 3 review rounds

Code Review

• Passed subagent code review
• Every finding answered