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/reference/workflow-fragments.md

@@ -261,7 +261,7 @@ no `msd:section` markers at all. An unmarked file composes to itself exactly;
 a marked file composes to itself minus the marker line bytes.
 
 Composition runs **before** the per-runtime converters (the `.claude/` →
-`.windsurf/`-style path and reference rewrites), so a marker's `id`/`when`
+`.cursor/`-style path and reference rewrites), so a marker's `id`/`when`
 attribute text is never exposed to a rewrite regex.
 
 ### Emission covers `agents/` too — gating does not
@@ -273,7 +273,7 @@ that emits agent content:
 
 | Emission path | Runtimes |
 |---|---|
-| `stageAgentsForRuntimeWithConverter` (with the raw `agents` kind and the Kimi agent kind routed through it) | the descriptor-driven runtimes, plus `claude` local and `zcode` |
+| `stageAgentsForRuntimeWithConverter` (with the raw `agents` kind routed through it) | the descriptor-driven runtimes, plus `claude` local and `zcode` |
 | `bin/install.js`'s inline agent loop | every non-descriptor runtime |
 | `installCodexConfig`'s per-agent `.toml` writer | `codex` |