feat(cli): add 'hf agent status' wrapper for POST /calendar/agent/status

The plan-schedule workflow needs to report agent runtime status
(idle/busy/on_call/exhausted/offline) at the end of planning, but the
cli had no wrapper for this — workflows were dropping inline curl in
the middle of their procedure to hit the backend.

This adds 'hf agent status --set <status> [--reason ...] [--recovery-at ...]'.
The endpoint identifies the agent purely from X-Agent-ID + X-Claw-Identifier
headers (no token), so the cli reads AGENT_ID from env and falls back
to hostname() for CLAW_IDENTIFIER if it isn't set — same convention
the openclaw plugin uses. Refuses to send if AGENT_ID env is missing,
since this only makes sense from a pcexec/agent runtime context.

Surface entry added so 'hf --help' lists it.

🤖 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

@@ -29,6 +29,13 @@ func CommandSurface() []Group {
 		{Name: "version", Description: "Show CLI version", Permitted: true},
 		{Name: "health", Description: "Check API health", Permitted: true},
 		{Name: "config", Description: "View and manage CLI configuration", Permitted: true},
+		{
+			Name:        "agent",
+			Description: "Runtime status reporting for the calling agent (uses AGENT_ID/CLAW_IDENTIFIER env)",
+			SubCommands: []Command{
+				{Name: "status", Description: "Report runtime status: hf agent status --set <idle|busy|on_call|exhausted|offline>", Permitted: true},
+			},
+		},
 		{
 			Name:        "user",
 			Description: "Manage users",