Add persistent global Codex context audit

[pfedotovsky]

Summary:

• add a secret-safe read-only inventory for persistent global Codex context
• generate a separate daily companion automation prompt and specification
• document the workflow and install it into private control projects

Safety:

• excludes session transcripts and secret-bearing config values
• reports suggestions only and never edits global configuration
• keeps Desktop state and plugin caches distinct from injected prompt context

Validation:

• 35 engine tests
• 4 installer tests
• built-in skill validator
• public-tree security scan
• system skill and plugin validators