fix(codex): review fixes — envelope handling, mode guards, UI parity

Blocker: runCodex read raw response shapes, but the global
preSerialization hook (server.ts) wraps every payload in the
{ success, data } envelope — status.available was always undefined, so
the UI unconditionally printed "Codex CLI not found" and could never
start a session; the created session was also never auto-selected
(data.sessionId vs data.data.sessionId). Fixed both reads to match
runOpenCode, and updated the test mocks to the real wire shape (plus a
selectSession assertion) so envelope drift fails the test.

Guard parity: export isExternalCliMode() from session.ts and use it in
the ralph-config guard, all three respawn guards, and the six restore/
setup guards in server.ts that previously only excluded 'opencode' —
codex sessions could otherwise get a Ralph tracker or respawn
controller attached (idle detection is Claude-specific and output-
silence respawn cycling would misfire on a quiet codex TUI).

UI parity: cx tab badge, "Kill Tmux & Codex" dialog title, and the
missing CSS (.run-mode-dot.codex, .tab-mode.codex, .mode-codex button
colors — purple) so the Codex menu dot is no longer invisible. Removed
the dead object-literal runMode getter that Object.assign flattens
(superseded by the defineProperty accessor this PR adds).

Verified end-to-end on an isolated instance with a stub codex binary:
10/10 Playwright checks (menu/dot/label/button styling, session
created + auto-selected, cx badge, TUI output streamed, ralph+respawn
guards reject codex) and --dangerously-bypass-approvals-and-sandbox
+ --model observed on the spawned command line.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/web/routes/ralph-routes.ts

@@ -9,7 +9,7 @@ import { join, dirname, resolve, relative, isAbsolute } from 'node:path';
 import { existsSync, mkdirSync, writeFileSync } from 'node:fs';
 import fs from 'node:fs/promises';
 import { ApiErrorCode, createErrorResponse, getErrorMessage, type ApiResponse } from '../../types.js';
-import { Session } from '../../session.js';
+import { Session, isExternalCliMode } from '../../session.js';
 import { RespawnController } from '../../respawn-controller.js';
 import { RalphConfigSchema, FixPlanImportSchema, RalphPromptWriteSchema, RalphLoopStartSchema } from '../schemas.js';
 import { SseEvent } from '../sse-events.js';
@@ -44,9 +44,12 @@ export function registerRalphRoutes(
     };
     const session = findSessionOrFail(ctx, id);
 
-    // Ralph tracker is not supported for opencode sessions
-    if (session.mode === 'opencode') {
-      return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Ralph tracker is not supported for opencode sessions');
+    // Ralph tracker is not supported for external-CLI sessions (opencode/codex)
+    if (isExternalCliMode(session.mode)) {
+      return createErrorResponse(
+        ApiErrorCode.INVALID_INPUT,
+        `Ralph tracker is not supported for ${session.mode} sessions`
+      );
     }
 
     // Handle reset first (before other config)

src/web/routes/respawn-routes.ts

@@ -11,6 +11,7 @@ import { SseEvent } from '../sse-events.js';
 import { findSessionOrFail, autoConfigureRalph, parseBody } from '../route-helpers.js';
 import type { SessionPort, EventPort, RespawnPort, ConfigPort, InfraPort } from '../ports/index.js';
 import { getLifecycleLog } from '../../session-lifecycle-log.js';
+import { isExternalCliMode } from '../../session.js';
 import {
   AI_CHECK_MODEL,
   AI_IDLE_CHECK_MAX_CONTEXT,
@@ -88,9 +89,9 @@ export function registerRespawnRoutes(
     }
     const session = findSessionOrFail(ctx, id);
 
-    // Respawn is not supported for opencode sessions
-    if (session.mode === 'opencode') {
-      return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Respawn is not supported for opencode sessions');
+    // Respawn is not supported for external-CLI sessions (opencode/codex)
+    if (isExternalCliMode(session.mode)) {
+      return createErrorResponse(ApiErrorCode.INVALID_INPUT, `Respawn is not supported for ${session.mode} sessions`);
     }
 
     // Create or get existing controller
@@ -231,9 +232,9 @@ export function registerRespawnRoutes(
       return createErrorResponse(ApiErrorCode.SESSION_BUSY, 'Session is busy');
     }
 
-    // Respawn is not supported for opencode sessions
-    if (session.mode === 'opencode') {
-      return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Respawn is not supported for opencode sessions');
+    // Respawn is not supported for external-CLI sessions (opencode/codex)
+    if (isExternalCliMode(session.mode)) {
+      return createErrorResponse(ApiErrorCode.INVALID_INPUT, `Respawn is not supported for ${session.mode} sessions`);
     }
 
     try {
@@ -296,9 +297,9 @@ export function registerRespawnRoutes(
     const body = reResult.data as { config?: Partial<RespawnConfig>; durationMinutes?: number };
     const session = findSessionOrFail(ctx, id);
 
-    // Respawn is not supported for opencode sessions
-    if (session.mode === 'opencode') {
-      return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Respawn is not supported for opencode sessions');
+    // Respawn is not supported for external-CLI sessions (opencode/codex)
+    if (isExternalCliMode(session.mode)) {
+      return createErrorResponse(ApiErrorCode.INVALID_INPUT, `Respawn is not supported for ${session.mode} sessions`);
     }
 
     // Check if session is running (has a PID)