feat: add Qoder hooks support (UserPromptSubmit + PreToolUse) (#529)

* feat: add Qoder hooks support (UserPromptSubmit + PreToolUse)

- Add isQoder detection via QODER_SESSION_ID in ponytail-runtime.js
- Add UserPromptSubmit double-duty: auto-activate + ruleset injection
- Add PreToolUse hook with task|Task matcher for subagent injection
- Create hooks/qoder-hooks.json reference template
- Update .qoder-plugin/plugin.json with hooks field
- Add .qoder/rules/ponytail.md for per-project rules
- Add comprehensive tests for Qoder runtime behavior
- Update README.md and docs/agent-portability.md

* check-versions: enforce .qoder-plugin/plugin.json version too

---------

Co-authored-by: shiding <shiding@ruigushop.com>
Co-authored-by: Emeriko <dietrich.gebert@gmail.com>