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.

src/init.cts

@@ -4288,7 +4288,7 @@ function cmdAgentSkills(
   );
 
   // #2454: Agent prompt fallback for AGENTS-native runtimes where named
-  // subagents are NOT dispatchable (kimi-code, kimi, opencode, kilo, etc.).
+  // subagents are NOT dispatchable (opencode, etc.).
   // On these runtimes, workflows inject ${AGENT_SKILLS_*} into the dispatch
   // prompt of a built-in subagent (coder/explore/plan). If no
   // model_profile_overrides or agent_skills config entry exists, the block
@@ -4638,7 +4638,7 @@ function buildSkillManifest(cwd: string, skillsDir: string | null = null): Skill
       }
 
       // Nested layout: <entry>/skills/<stem>/SKILL.md
-      // Used by cline, qwen, hermes, augment, trae, antigravity (#69 nested=true).
+      // Used by runtimes whose skills layout declares nesting (#69 nested=true).
       // Descend exactly one level into <entry>/skills/ — no deeper recursion.
       // Scope to msd-ns-* routers only: never vacuum up an unrelated user skill
       // that happens to have its own `skills/` subdirectory.