Count skills Codex loads by printing SKILL.md

[0xCardinal]

Problem

Codex has no Skill tool. It loads a skill with a shell command like cat ~/.agents/skills/code-review/SKILL.md. Extension usage only counted Skill tool calls and SKILL.md reads through file tools, so Codex skill use never showed up (e.g. Codex session 01a1056e-0eb9-7d11-8b11-0f70c7128c0d loaded code-review, i-have-adhd and unslop in one cat; none registered).

Change

• Shell commands that print SKILL.md files (cat/sed/head/…, also via rtk proxy or sh -c) count as skill reads. The full command comes from detail.command when the stored target is clipped at 120 chars. Writing, listing or grepping a skill file does not count.
• One command can load several skills, so extension_uses is keyed by (event_id, ord). The table is derived from events, so _migrate drops and recreates it; USAGE_VERSION bump refills it.
• Shell reads use via: "read", so they still fold into a nearby Skill tool load instead of double counting.

Testing

• New test_codex_shell_skill_reads_count_as_loads; full backend suite passes (404), ruff clean.
• Migration checked on a DB with the old schema; re-running init is a no-op.
• Dry run on a real 2 GB DB: 208 shell skill reads found (mostly Codex); sync filter query takes ~1.3s.

🤖 Generated with Claude Code