Implement coder task logs (alias log) to view task logs.

Scope

• Usage: coder task logs <task> [--follow] [--tail N]
• Use shared <task> resolver.
• Fetch via GET /tasks/{id}/logs with follow/tail.
  • (Optionally direct connect to agentapi to retrieve history/output to reduce coderd load.)

Depends on: #891, #901

References: #838