fix(runtime): strip reintroduced Anthropic routing env

Prevent settings-profile Claude launches from reintroducing
routing/auth env after the final env merge.

- re-strip ANTHROPIC_BASE_URL, ANTHROPIC_AUTH_TOKEN, and
  ANTHROPIC_API_KEY after merging envVars
- preserve model-selection env such as ANTHROPIC_MODEL and
  ANTHROPIC_DEFAULT_SONNET_MODEL
- add a regression test covering explicit settings-profile
  overrides that try to reintroduce routing env

Verification:
- bun test tests/unit/utils/claudecode-env-stripping.test.ts
- bun run validate

src/utils/shell-executor.ts

@@ -177,10 +177,13 @@ export function execClaude(
   const mergedEnv = envVars
     ? { ...baseEnv, ...claudeLaunchEnv, ...envVars, ...webSearchEnv }
     : { ...baseEnv, ...claudeLaunchEnv, ...webSearchEnv };
+  const effectiveMergedEnv = stripInheritedAnthropicRoutingEnv
+    ? stripAnthropicRoutingEnv(mergedEnv)
+    : mergedEnv;
 
   // Strip Claude Code nested session guard env var to allow CCS delegation
   // (Claude Code v2.1.39+ sets CLAUDECODE to detect nested sessions)
-  const env = stripClaudeCodeEnv(mergedEnv);
+  const env = stripClaudeCodeEnv(effectiveMergedEnv);
 
   if (profileType !== 'account') {
     try {