fix: resolve TypeScript type errors and add tsc check to CI

[ChenNima]

Summary

• Fix all 27 tsc --noEmit type errors across 7 test files and 1 mock file
• Add npx tsc --noEmit step to GitHub Actions CI workflow (runs after Prisma generate, before tests)

Changed files

File	Change
.github/workflows/test.yml	Add Type check step with npx tsc --noEmit
src/lib/__mocks__/prisma.ts	Fix import: @prisma/client → @/generated/prisma/client
src/lib/__tests__/api-handler.test.ts	Cast process.env to bypass NODE_ENV read-only
src/lib/__tests__/auth.test.ts	Add as unknown as UserAuthContext for agent mock values passed to getUserSessionFromRequest
src/lib/__tests__/cookie-utils.test.ts	Use Record<string, string | undefined> alias for process.env mutations
src/lib/__tests__/event-bus.test.ts	Add type assertions for messageHandler calls
src/services/__tests__/assignment.service.test.ts	Remove userUuid/agentUuid properties not in AuthContext (12 occurrences)
src/services/__tests__/comment.service.test.ts	Cast "unknown" to "task" for invalid TargetType test

Test plan

• npx tsc --noEmit passes locally with 0 errors
• CI workflow runs type check and tests successfully

Generated with Claude Code

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	96.19% (🎯 95%)	1743 / 1812
🔵	Statements	95.14% (🎯 95%)	1881 / 1977
🔵	Functions	94.72% (🎯 93%)	377 / 398
🔵	Branches	86.99% (🎯 85%)	1177 / 1353

File Coverage

No changed files found.

Generated in workflow #49 for commit 4b4a8d2 by the Vitest Coverage Report Action