refactor(frontend): simplify leaf component state

[aksOps]

Summary

• simplify leaf-component keyboard and status state handling without changing behavior
• replace nested conditional rendering in Card AI and integrations with named state values
• add characterization coverage for keyboard propagation, busy states, token removal, and stale same-key integration completions

Sonar scope

Closes five maintainability findings in CardAIDraft.tsx, IntegrationsSection.tsx, and LabelsCombobox.tsx.

Verification

• targeted Vitest: 24/24
• full frontend: 932/932
• frontend coverage: 98.30% statements, 95.25% branches, 98.77% functions, 99.46% lines
• build and TypeScript: pass
• Go coverage 97.8%, race, vet, format: pass
• Actionlint and ShellCheck: pass
• browser differential: 6/6 scenarios byte-identical, 0 changed pixels

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
97.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud