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/explanation/context-engineering.md

@@ -77,7 +77,6 @@ Since MSD 1.4.0, this is addressed by registering runtime lifecycle hooks. Rathe
 Each AI runtime exposes lifecycle events in its own vocabulary, but the purpose is the same across all of them: fire at boundaries that correspond to context pressure or turn transitions, so MSD can observe and react.
 
 - **Claude Code** fires `PreCompact` when a compaction is about to occur, `Stop` when a session turn ends, and `SubagentStop` when a spawned subagent completes. Together these bracket the moments when context has grown or a context-consuming task has just finished.
-- **Qwen** exposes `SubagentStop`, `Stop`, and `PreCompact`, mirroring Claude Code's shape in its own event system.
 
 Think of these as the same concept — "notify MSD at context boundaries" — expressed in each runtime's native event vocabulary. This is the multi-runtime philosophy applied at the observability layer: MSD registers the semantically equivalent hook wherever each runtime exposes it, rather than demanding every runtime adopt a single event schema.