feat(adapters/gemini-local): add auth detection, turn-limit handling, sandbox, and approval modes

Incorporate improvements from PR #13 and #105 into the gemini-local adapter:

- Add detectGeminiAuthRequired() for runtime auth failure detection with
  errorCode: "gemini_auth_required" on execution results
- Add isGeminiTurnLimitResult() to detect exit code 53 / turn_limit status
  and clear session to prevent stuck sessions on next heartbeat
- Add describeGeminiFailure() for structured error messages from parsed
  result events including errors array extraction
- Return parsed resultEvent in resultJson instead of raw stdout/stderr
- Add isRetry guard to prevent stale session ID fallback after retry
- Replace boolean yolo with approvalMode string (default/auto_edit/yolo)
  with backwards-compatible config.yolo fallback
- Add sandbox config option (--sandbox / --sandbox=none)
- Add GOOGLE_GENAI_USE_GCA auth detection in environment test
- Consolidate auth detection regex into shared detectGeminiAuthRequired()
- Add gemini-2.0-flash and gemini-2.0-flash-lite model IDs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/adapters/gemini-local/src/ui/build-config.ts

@@ -67,7 +67,8 @@ export function buildGeminiLocalConfig(v: CreateConfigValues): Record<string, un
     }
   }
   if (Object.keys(env).length > 0) ac.env = env;
-  if (v.dangerouslyBypassSandbox) ac.yolo = true;
+  if (v.dangerouslyBypassSandbox) ac.approvalMode = "yolo";
+  ac.sandbox = !v.dangerouslyBypassSandbox;
   if (v.command) ac.command = v.command;
   if (v.extraArgs) ac.extraArgs = parseCommaArgs(v.extraArgs);
   return ac;