refactor: drop 12 runtimes, keep Claude, Codex, OpenCode, Cursor, ZCode, Antigravity

Removes kilo, kimi, kimi-code, copilot, windsurf, augment, trae, qwen, hermes,
cline, codebuddy and pi end to end: capability descriptors, installer branches
and converters (bin/install.js 14.9k -> 11.2k lines), TypeScript converters,
hook surfaces and runtime homes, review lanes qwen/kimi-code, the two pi
migrations, Kimi payload normalization in the hook guards, dead hostBehaviors
vocabulary, launcher home probes, fixtures, runtime-specific tests and the
prose that presented them as supported.

Installer output for the six kept runtimes is byte-identical to before the
prune. The Kimi tool-vocabulary tests in workflow-guard, read-guard and
read-injection-scanner are left in place pending a decision.

docs/BETA.md

@@ -29,7 +29,7 @@ When you're satisfied with the draft, you save it and import it back into MSD
 
 ### Requirements
 
-- **Runtime:** Claude Code only. The command exits with an error on Antigravity CLI, Copilot CLI, and other runtimes.
+- **Runtime:** Claude Code only. The command exits with an error on Antigravity CLI and other runtimes.
 - **Version:** Claude Code v2.1.91 or later (the `$CLAUDE_CODE_VERSION` env var must be set).
 - **Cost:** No extra charge for Pro and Max subscribers. Ultraplan is included at no additional cost.