Restore Gaasbot CTO voice from the GaaS original, keep it off

[TheGreatAxios]

Summary

• Restore the Gaasbot CTO voice (git discipline, architecture opinions, tech preferences, push-back versus flexible, how to respond) ported from the GaaS original onto the existing risk-counsel lane, with no new gate, implement, or spawn powers
• Add style to optionalSkills alongside philosophy and native-integration
• Port from the local HEAD copy of abklabs/agents plugins/gaas/agents/gaasbot.md since 6e16b6c is not resolvable locally

Verification

• bun test src/agent/directors/gaasbot/ passes (15 pass, 0 fail)
• bun run lint, bun run typecheck, and bun run build pass
• Full bun run check test phase fails on 368 unrelated tests with zero gaasbot failures; the same files pass in isolation and the host disk reports 100% full, so the failures are environmental and unrelated to this change

Fixes CL-7663

[linear-code]

CL-7663