fix: address PR review findings for Gemini run mode + Ralph todo-config

Gemini (PR #134) blockers:
- runGemini() now unwraps the {success,data} envelope: status check reads
  .data.available, quick-start reads data.data.sessionId (was reading the raw
  shape, so the Run-Gemini button could never start a session).
- setGeminiEnvVars() now uses the socket-scoped ${this.tmux()} setenv instead of
  bare tmux — Gemini/Google auth env vars were targeting the wrong tmux server
  and silently failing on every install.

Gemini parity polish:
- gemini tab-mode badge ('gm') + .tab-mode.gemini CSS; kill-dialog label
  'Kill Tmux & Gemini'; codeman doctor dependency-registry entry; export
  isGeminiAvailable from utils barrel; COLORTERM=truecolor + unset NO_COLOR;
  add gemini to isAltScreenStripMode (Ink TUI, repaints inline like Codex/Claude).
- Revert 4 system-routes.test.ts envelope assertions weakened to
  (body.message ?? body.error) back to (body.success === false).
- Add a runGemini() vm-sandbox test that drives the envelope path end-to-end.

Ralph todo-config (PR #135): maxTodos/todoExpirationMinutes are now persisted
and read back — surfaced via the loopState getter (RalphTrackerState) into
toState()/SSE broadcast and restored in restoreState(), mirroring maxIterations.

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

src/web/public/styles.css

@@ -1178,6 +1178,11 @@ body.solo-mode .btn-lifecycle-log {
   color: #a855f7;
 }
 
+.session-tab .tab-mode.gemini {
+  background: rgba(138, 180, 248, 0.2);
+  color: #8ab4f8;
+}
+
 /* Timer Banner - Compact */
 .timer-banner {
   display: flex;