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.

msd-core/workflows/execute-phase.md

@@ -15,16 +15,11 @@ Orchestrator coordinates, not executes. Each subagent loads the full execute-pla
 
 <!-- #2508 runtime-aware-dispatch -->
 
-> **Runtime-aware dispatch (#2508 Phase 4).** MSD workflows dispatch specialized subagents by role. Before dispatching on a built-in-only runtime (kimi-code — three built-ins only), resolve the role to a built-in via `msd_run query resolve-dispatch-type --requested <role> --raw`. On named-dispatch runtimes (Claude/OpenCode/…) the role is returned unchanged; on kimi-code it maps to `coder`/`explore`/`plan` by role-suffix. The persona rides `${AGENT_SKILLS_<ROLE>}` (Phase 3) regardless. See @msd-core/references/runtime-aware-dispatch.md.
+> **Runtime-aware dispatch (#2508 Phase 4).** MSD workflows dispatch specialized subagents by role. Before dispatching on a built-in-only runtime (three built-ins only), resolve the role to a built-in via `msd_run query resolve-dispatch-type --requested <role> --raw`. On named-dispatch runtimes (Claude/OpenCode/…) the role is returned unchanged; on built-in-only runtimes it maps to `coder`/`explore`/`plan` by role-suffix. The persona rides `${AGENT_SKILLS_<ROLE>}` (Phase 3) regardless. See @msd-core/references/runtime-aware-dispatch.md.
 
 <runtime_compatibility>
 **Subagent spawning is runtime-specific:**
 - **Claude Code:** Uses `Agent(subagent_type="msd-executor", ...)` — backgrounded by default; verify completion
-- **Copilot:** Subagent spawning does not reliably return completion signals. **Default to
-  sequential inline execution**: read and follow execute-plan.md directly for each plan
-  instead of spawning parallel agents. Only attempt parallel spawning if the user
-  explicitly requests it — and in that case, rely on the spot-check fallback in step 3
-  to detect completion.
 - **Codex:** native subagent sessions can end abnormally (`turn_aborted`) after the plan
   work is already committed. Completion is decided by the step-4 artifact reconciliation
   (SUMMARY + matching recent commits), not by the session's terminal state (#4217).
@@ -161,14 +156,6 @@ When `CONTEXT_WINDOW < 200000` (sub-200K models), subagent prompts are thinned t
 
 When `parallelization` is false, plans within a wave execute sequentially.
 
-**Runtime detection for Copilot:**
-Check if the current runtime is Copilot by testing for the `@msd-executor` agent pattern
-or absence of the `Agent()` subagent API. If running under Copilot, force sequential inline
-execution regardless of the `parallelization` setting — Copilot's subagent completion
-signals are unreliable (see `<runtime_compatibility>`). Set `COPILOT_SEQUENTIAL=true`
-internally and skip the `execute_waves` step in favor of `check_interactive_mode`'s
-inline path for each plan.
-
 **REQUIRED — Sync chain flag with intent.** If user invoked manually (no `--auto`), clear the ephemeral chain flag from any previous interrupted `--auto` chain. This prevents stale `_auto_chain_active: true` from causing unwanted auto-advance. This does NOT touch `workflow.auto_advance` (the user's persistent settings preference). You MUST execute this bash block before any config reads:
 ```bash
 # REQUIRED: prevents stale auto-chain from previous --auto runs
@@ -1035,7 +1022,7 @@ increases monotonically across waves. `{status}` is `complete` (success),
    RETRY_AFTER=$(echo "$CLASS_JSON" | jq -r '.retryAfterSeconds // empty')
    if [ -n "$RETRY_AFTER" ]; then RETRY_HINT="  Provider hinted retry-after: ${RETRY_AFTER}s"; else RETRY_HINT=""; fi
    ```
-   One classifier branch handles sentinels across Claude/Copilot/Codex/Antigravity. Reference: `docs/research/provider-rate-limit-signals.md`.
+   One classifier branch handles sentinels across Claude/Codex/Antigravity. Reference: `docs/research/provider-rate-limit-signals.md`.
    **Abnormal ends reconcile first (#4217):** an abnormal session end (`turn_aborted`-class) routes through the step-4 artifact reconciliation BEFORE classifying the failure — artifacts decide.
    **Step 7.1 — `class == "quota-exceeded"`:** follow the quota-recovery fragment below.
    **Step 7.2 — `class == "classify-handoff-bug"`:**