Improve cleanup blocker follow-up reports

[chubes4]

Summary

• Add bucket-specific, non-destructive follow-up commands for cleanup blockers: dirty_worktree, unpushed_commits, stale_worktree_marker, and primary_missing.
• Surface narrow evidence commands in both task-backed cleanup status summaries and direct worktree cleanup skipped_next_commands.
• Extend focused cleanup CLI smoke coverage for status, evidence, JSON, and human output paths.

Fixes #646

Verification

• php -l inc/Cleanup/CleanupRemainingWorkSummary.php
• php -l inc/Workspace/WorkspaceWorktreeCleanupEngine.php
• php -l tests/smoke-worktree-cleanup-cli.php
• php tests/smoke-worktree-cleanup-cli.php

Notes

• The new recommended commands are read-only or dry-run previews by default.
• Broader php tests/smoke-worktree-cleanup.php was not used as a gate for this slice because it currently reports duplicate skipped-row fixture assertions unrelated to these focused output changes.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Implementing the cleanup follow-up command mapping, updating focused smoke coverage, and running targeted verification. Chris remains responsible for review and merge.