Expose standalone workspace inventory without WordPress

[chubes4]

Summary

• add bounded standalone workspace inventory and exact-handle show operations
• report local Git/filesystem observations separately from unavailable WordPress lifecycle state
• document the database-outage recovery route in generated agent guidance
• cover pagination, exact lookup, hard bounds, and read-only behavior with real Git fixtures

Closes #1319.

Verification

• php tests/standalone-worktree-provider.php
• php tests/standalone-worktree-provider-command.php
• php tests/worktree-command-help-snapshots.php
• php tests/smoke-agents-md-sections.php
• php tests/standalone-workspace-inventory.php
• PHP syntax checks on the changed provider, executable, and fixture

AI Assistance

OpenAI GPT-5.6 Sol via OpenCode implemented the bounded standalone provider operations and tests. OpenAI GPT-5.6 Sol via OpenCode then independently reviewed the diff and reran focused verification under Chris Huber's direction.