fix(cli): release workspace resources after success

[chubes4]

Summary

• finalize synchronous workspace WP-CLI requests at the command-owning after_invoke boundary
• flush terminal streams, clear deferred WordPress shutdown work, and close the request-owned database connection only after successful command return
• replace synthetic list-only exit coverage with process-level worktree finalize coverage using a merged-PR-shaped receipt and owner-terminal-outcome=success

Root Cause

The existing boundary deferred resource release until WordPress shutdown. A successful finalizer could commit metadata and render its receipt while the request-owned database connection remained open; a later shutdown participant could then retain the process and its SQLite lock. The regression fixture verifies current-main behavior deterministically by making that later participant wait only while the DB remains open.

The shared workspace after_invoke callback is the smallest generic owning layer: it runs after successful command output and before PHP shutdown, while failures before after_invoke retain the normal shutdown lifecycle and nonzero status.

Closes #1234.

Verification

Passed:

• php tests/workspace-cli-bounded-exit.php
• php tests/workspace-command-startup-bounds.php
• php tests/workspace-help-cli-lifecycle.php
• php tests/workspace-list-cli-format-contract.php
• php tests/workspace-show-cli-format-contract.php
• changed-file php -l checks
• git diff origin/main...HEAD --check
• every standalone tests/*.php test except the unchanged baseline failure below

The full standalone loop stops at tests/worktree-add-lifecycle.php with partial success omitted its exact read-only continuation. The same environment-sensitive failure is documented on current main in PR #1198, and this PR does not modify that test or the implicated handoff lifecycle. Rerunning all standalone tests while skipping only that baseline test passes. worktree-command-wp-cli-synopsis.php reports its existing skip because WP_CLI_ROOT is unavailable.

AI Assistance

OpenAI GPT-5.6 Sol via OpenCode read the issue and history, traced the removed process-boundary coverage, implemented the owning-layer resource finalizer and process fixture, and ran the verification above. Chris Huber directed the work and remains responsible for the change.