feat(#164): Add database schema for job tracking

Add Prisma schema for runner jobs, job steps, and job events to support
the autonomous runner infrastructure (M4.2).

Enums added:
- RunnerJobStatus: PENDING, QUEUED, RUNNING, COMPLETED, FAILED, CANCELLED
- JobStepPhase: SETUP, EXECUTION, VALIDATION, CLEANUP
- JobStepType: COMMAND, AI_ACTION, GATE, ARTIFACT
- JobStepStatus: PENDING, RUNNING, COMPLETED, FAILED, SKIPPED

Models added:
- RunnerJob: Top-level job tracking linked to workspace and agent_tasks
- JobStep: Granular step tracking within jobs with phase organization
- JobEvent: Immutable event sourcing audit log for jobs and steps

Foreign key relationships:
- runner_jobs → workspaces (workspace_id, CASCADE)
- runner_jobs → agent_tasks (agent_task_id, SET NULL)
- job_steps → runner_jobs (job_id, CASCADE)
- job_events → runner_jobs (job_id, CASCADE)
- job_events → job_steps (step_id, CASCADE)

Indexes added for performance on workspace_id, status, priority, timestamp.

Migration: 20260201205935_add_job_tracking

Quality gates passed: typecheck, lint, build

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/scratchpads/164-database-schema-jobs.md

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+# Issue #164: Database schema for job tracking
+
+## Objective
+
+Add Prisma schema for runner_jobs, job_steps, and job_events tables to support the autonomous runner infrastructure.
+
+## Approach
+
+1. Read existing schema.prisma to understand current conventions
+2. Add four enums: RunnerJobStatus, JobStepPhase, JobStepType, JobStepStatus
+3. Add three models: RunnerJob, JobStep, JobEvent
+4. Create and run migration
+5. Verify migration succeeds
+
+## Schema Design
+
+### Enums
+
+- **RunnerJobStatus**: PENDING, QUEUED, RUNNING, COMPLETED, FAILED, CANCELLED
+- **JobStepPhase**: SETUP, EXECUTION, VALIDATION, CLEANUP
+- **JobStepType**: COMMAND, AI_ACTION, GATE, ARTIFACT
+- **JobStepStatus**: PENDING, RUNNING, COMPLETED, FAILED, SKIPPED
+
+### Models
+
+1. **RunnerJob** - Top-level job tracking
+   - Links to workspace and optionally to agent_task
+   - Tracks overall job status, progress, result
+   - Timestamps: created_at, started_at, completed_at
+
+2. **JobStep** - Granular step tracking
+   - Child of RunnerJob
+   - Phase-based organization (SETUP, EXECUTION, etc.)
+   - Token tracking for AI operations
+   - Duration tracking
+
+3. **JobEvent** - Event sourcing audit log
+   - Immutable event log for jobs and steps
+   - Links to both job and optionally step
+   - Actor tracking for accountability
+
+## Progress
+
+- [x] Read existing schema.prisma
+- [x] Read architecture document for schema requirements
+- [x] Add enums (RunnerJobStatus, JobStepPhase, JobStepType, JobStepStatus)
+- [x] Add RunnerJob model with workspace and agentTask relations
+- [x] Add JobStep model with job relation
+- [x] Add JobEvent model with job and step relations
+- [x] Add RunnerJob[] to Workspace and AgentTask relations
+- [x] Create migration (20260201205935_add_job_tracking)
+- [x] Test migration - all tables created successfully
+- [x] Run quality gates (typecheck, lint, build - all passed)
+- [x] Generate Prisma client
+- [ ] Commit changes
+
+## Schema Observations from Existing Code
+
+**Conventions Identified:**
+
+- UUID primary keys with `@db.Uuid` annotation
+- snake_case for database column names via `@map`
+- snake_case for table names via `@@map`
+- Timestamps use `@db.Timestamptz` for timezone awareness
+- workspace_id on all workspace-scoped tables with cascading deletes
+- Composite unique constraints with `@@unique([id, workspaceId])`
+- Consistent indexing patterns: workspace_id, status, timestamps
+- Json fields for flexible metadata with `@default("{}")`
+- Optional foreign keys use `@db.Uuid` without NOT NULL
+- Relations use descriptive names in both directions
+
+## Testing
+
+Since this is a schema-only change, testing will verify:
+
+- Migration runs successfully ✅
+- Foreign key constraints are valid ✅
+- Schema matches architecture document ✅
+
+Verification performed:
+
+1. Database tables created: runner_jobs, job_steps, job_events
+2. All enums created: RunnerJobStatus, JobStepPhase, JobStepType, JobStepStatus
+3. Foreign key relationships verified:
+   - runner_jobs → workspaces (workspace_id)
+   - runner_jobs → agent_tasks (agent_task_id, optional)
+   - job_steps → runner_jobs (job_id)
+   - job_events → runner_jobs (job_id)
+   - job_events → job_steps (step_id, optional)
+4. Indexes created for performance:
+   - workspace_id for workspace filtering
+   - status for job querying
+   - priority for job prioritization
+   - timestamp for event ordering
+5. Quality gates passed:
+   - TypeScript compilation ✅
+   - ESLint checks ✅
+   - NestJS build ✅
+   - Prisma client generation ✅
+
+## Notes
+
+- Following existing patterns from schema.prisma
+- Using UUID for all primary keys (existing convention)
+- Using snake_case for table names (Prisma convention)
+- All workspace-scoped tables include workspace_id for RLS
+- Migration file created: 20260201205935_add_job_tracking
+- Database push successful, migration marked as applied
+- Schema format validated successfully