…ture

Issue #22 — apc doctor:
New command that runs a series of health checks and prints a formatted
Rich report covering:
- Python version check (>= 3.12 required)
- Cache and config directory existence/write access
- OS keychain availability (shows backend name)
- age binary for export/import encryption
- LLM configuration status
- Cache counts (skills, MCP servers, memory entries)
- Detected AI tools

Each check shows ✓ (green) or ✗ (red) with a remediation hint for failures.

Issue #46 — apc install --list explains repo structure when no skills found:
When '--list' finds no skills, the output now includes the expected
repository layout:
  skills/<name>/SKILL.md  (required, with YAML frontmatter)
This prevents users from being stuck with a silent 'no skills found' message
when pointing at a non-skills repo.