feat(kiro): add IDC auth and endpoint improvements, redesign fingerprint system

- Add IAM Identity Center (IDC) authentication with CLI flags (--kiro-idc-login, --kiro-idc-start-url, --kiro-idc-region) and login flow
- Add ProfileArn auto-fetching in Execute/ExecuteStream for imported IDC accounts
- Simplify endpoint preference with map-based alias lookup and getAuthValue helper
- Redesign fingerprint as global singleton with external config and per-account deterministic generation
- Add StartURL and FingerprintConfig fields to Kiro config
- Add AgentContinuationID/AgentTaskType support in Kiro translators
- Add comprehensive tests for executor, fingerprint, SSO OIDC, and AWS helpers
- Add CLI login documentation to README

config.example.yaml

@@ -179,6 +179,8 @@ nonstream-keepalive-interval: 0
 #kiro:
 #  - token-file: "~/.aws/sso/cache/kiro-auth-token.json" # path to Kiro token file
 #    agent-task-type: "" # optional: "vibe" or empty (API default)
+#    start-url: "https://your-company.awsapps.com/start" # optional: IDC start URL (preset for login)
+#    region: "us-east-1" # optional: OIDC region for IDC login and token refresh
 #  - access-token: "aoaAAAAA..." # or provide tokens directly
 #    refresh-token: "aorAAAAA..."
 #    profile-arn: "arn:aws:codewhisperer:us-east-1:..."