fix(workspace): land delete_path impl + ability registration missed by #65

[chubes4]

Summary

Follow-up to #65, which shipped the wp datamachine-code workspace delete CLI subcommand but only the subcommand. The ability registration in WorkspaceAbilities.php and the delete_path() method in Workspace.php were silently dropped from the original commit.

Without this fix, wp datamachine-code workspace delete <repo> <path> errors with Workspace delete ability not available. because the CLI calls wp_get_ability('datamachine/workspace-delete') which isn't registered.

Root cause

The original git add --rel=A --rel=B --rel=C call against the workspace API only staged the first path silently. The CLI returned "Paths staged successfully" but git diff --cached confirmed only one file was staged. The other two files stayed dirty in the worktree, were never committed, and so never made it into the merged squash.

I'll file a separate DMC issue for the repeatable---rel bug; the workaround for now is one --rel per git add call.

What this PR adds

• Workspace::delete_path() (~115 LOC) — sits next to git_add and reuses its gate ladder: traversal, sensitive-path, allowlist, primary-mutation. Detects tracked vs untracked via git ls-files --error-unmatch and dispatches to either git rm [-r] or a recursive filesystem unlink.
• Workspace::remove_directory_recursive() — private helper that walks an untracked directory deepest-first.
• datamachine/workspace-delete ability registration in WorkspaceAbilities.php — input/output schemas, callback wiring to deletePath, and the deletePath static method.

Verification (live on intelligence-chubes4 — same scenarios as #65)

• Untracked file → unlink (1 path removed). ✓
• Tracked file → staged D entry in git status. ✓
• Directory without --recursive → directory_requires_recursive error. ✓
• Directory with --recursive → recursive unlink (N paths removed). ✓
• Sensitive path (.env) → sensitive_path error. ✓
• Path traversal (../escape) → invalid_path error. ✓
• Absolute path → invalid_path error. ✓
• Primary checkout without override → primary_mutation_not_allowed error. ✓
• Primary checkout with --allow-primary-mutation → succeeds. ✓
• Path not found → not_found (404) error. ✓

AI assistance

• AI assistance: Yes
• Tool(s): Claude Code (Sonnet 4.5)
• Used for: Spotting the missing pieces after pulling main locally to use the new primitive in a downstream homeboy refactor; identifying the --rel repeatable-stage bug as the root cause; reconstructing the dropped commit. Chris reviewed the missing-files framing and authorized the fix-up PR.