Manage state on agent beads for ZFC-compliant state reporting.

Agent beads (labeled gt:agent) can self-report their state using these commands.
This enables the Witness and other monitoring systems to track agent health.

States:
  idle      - Agent is waiting for work
  spawning  - Agent is starting up
  running   - Agent is executing (general)
  working   - Agent is actively working on a task
  stuck     - Agent is blocked and needs help
  done      - Agent completed its current work
  stopped   - Agent has cleanly shut down
  dead      - Agent died without clean shutdown (set by Witness via timeout)

Examples:
  bd agent state gt-emma running     # Set emma's state to running
  bd agent heartbeat gt-emma         # Update emma's last_activity timestamp
  bd agent show gt-emma              # Show emma's agent details

Usage:
  bd agent [command]

Available Commands:
  backfill-labels Backfill role_type/rig labels on existing agent beads
  heartbeat       Update agent last_activity timestamp
  show            Show agent bead details
  state           Set agent state

Flags:
  -h, --help   help for agent

Global Flags:
      --actor string              Actor name for audit trail (default: $BD_ACTOR, git user.name, $USER)
      --allow-stale               Allow operations on potentially stale data (skip staleness check)
      --db string                 Database path (default: auto-discover .beads/*.db)
      --dolt-auto-commit string   Dolt backend: auto-commit after write commands (off|on). Default from config key dolt.auto-commit
      --json                      Output in JSON format
      --lock-timeout duration     SQLite busy timeout (0 = fail immediately if locked) (default 30s)
      --no-auto-flush             Disable automatic JSONL sync after CRUD operations
      --no-auto-import            Disable automatic JSONL import when newer than DB
      --no-daemon                 Force direct storage mode, bypass daemon if running
      --no-db                     Use no-db mode: load from JSONL, no SQLite
      --profile                   Generate CPU profile for performance analysis
  -q, --quiet                     Suppress non-essential output (errors only)
      --readonly                  Read-only mode: block write operations (for worker sandboxes)
      --sandbox                   Sandbox mode: disables daemon and auto-sync
  -v, --verbose                   Enable verbose/debug output

Use "bd agent [command] --help" for more information about a command.