Explain residual uncertain macOS artifact process probes

[chubes4]

Problem

After the macOS process-probe repair in PR #985, artifact apply can still fail closed with active_process_probe_uncertain without enough evidence to distinguish a real process-inspection limitation from a remaining probe defect.

Evidence

A reviewed artifact plan included mcp-wordpress-remote@fix-103-oauth-initialize-timeout. Apply skipped it with:

active process use could not be authoritatively excluded; safe cleanup is failing closed

The same apply returned precise dirty and unpushed reasons for every other blocker, but no provider status, command failure, path count, timeout, or remediation for this uncertain probe.

Expected

Fail-closed behavior remains, but uncertainty is fully diagnosable and retryable.

Acceptance criteria

• Include process-probe provider, status, timeout/error, inspected path count, and candidate path in the skip row.
• Distinguish unavailable, timed out, permission denied, malformed output, and ambiguous process evidence.
• Print a bounded non-destructive retry/diagnostic command.
• Verify the post-Probe artifact processes on macOS #985 macOS path with a Node worktree and a no-process worktree.
• Preserve fail-closed cleanup semantics.