Optimize island idle rendering

[sparkleMing]

Summary

• Stop island wave/fin animation while neutral or no sessions are present.
• Run glow animation only for stopped/approval collapsed states.
• Shrink the collapsed island window while preserving glow overflow padding.

Validation

• npm run typecheck
• island inline script syntax check

Notes

• npm test currently fails on existing 5s timeout cases unrelated to the island changes: tests/agent-clis.test.ts, tests/install-tool.test.ts, tests/profile-orchestrator.test.ts, and tests/terminal.test.ts.