feat(cli): hf user create --agent-id/--claw-identifier + hf user bind-agent

Implements NEXT_WAVE_DEV_DIRECTION.md §7.3 (was 4 lines of spec, never
shipped). Backend's POST /users has accepted agent_id+claw_identifier
since BE-CAL-003 but the cli never sent them, so historically every
agent user (zhi/lyn/mirror/sherlock/orion/nav on prod today) was
created with only the user row — agents table left empty, and all
downstream calendar/heartbeat/schedule-type flows that go through
_require_agent() returned 404.

## hf user create — new flags

  --agent-id <id>
  --claw-identifier <id>

Both required together (matches backend invariant). Either can come
from pcexec env: AGENT_ID env for agent-id, `openclaw config get
plugins.harbor-forge.identifier` for claw-identifier. Partial pair is
treated as "neither" so plain user creation (no binding intended) still
works without a 400.

## hf user bind-agent <username> — NEW subcommand

Backfills agents row for an existing user. PATCH
/users/{username}/bind-agent. Same accept --agent-id/--claw-identifier
flags + pcexec env fallback. requireBoth=true here — fail loudly if
the pair can't be resolved since the whole command is the binding.

## Wiring

- userCreatePayload gains AgentID + ClawIdentifier omitempty fields
- new userBindAgentPayload struct (both required)
- resolveAgentBinding helper shared by both commands
- main.go user create case parses --agent-id/--claw-identifier;
  new user bind-agent case parses positional username + the same flags
- surface.go lists bind-agent so `hf user` and `hf --help` show it

Build: clean. Smoke-tested both subcommand usage strings.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/help/surface.go

@@ -48,6 +48,7 @@ func CommandSurface() []Group {
 				{Name: "deactivate", Description: "Deactivate a user", Permitted: has(perms, "user.manage")},
 				{Name: "delete", Description: "Delete a user", Permitted: has(perms, "user.manage")},
 				{Name: "reset-apikey", Description: "Reset a user's API key", Permitted: true},
+				{Name: "bind-agent", Description: "Backfill the agents row for an existing user (acc-mgr token; use --agent-id / --claw-identifier or AGENT_ID env)", Permitted: true},
 			},
 		},
 		{