Tasks: Database migrations for task lifecycle

[mafredri]

Repo: coder/coder

Scope: Add schema support for log snapshots and task-specific build reasons.

Changes:

• Create task_snapshots table (consider UNLOGGED; data is ephemeral, best-effort, regenerated on each pause):
  • task_id UUID PRIMARY KEY REFERENCES tasks(id) ON DELETE CASCADE
  • log_snapshot JSONB NOT NULL
    • Wrapper schema: {"format":"agentapi","data":<raw_agentapi_payload>}
  • log_snapshot_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
• Add build reason enum values: task_auto_pause, task_manual_pause, task_resume

Files:

• New migration in coderd/database/migrations/
• coderd/database/dump.sql
• Run make gen
• Update enterprise/audit/table.go if needed

Acceptance criteria:

• Migration runs without error on fresh and existing databases
• make gen succeeds
• make lint passes
• Build reasons available in database.BuildReason enum

Dependencies: None

References:

• PRD: Start/Pause/Resume the Task Workspace
• RFC: Tasks: Start/Pause/Resume Lifecycle: Database Changes