feat: PXE debug boot mode for rescue/diagnostics

New `labctl provision debug <target>` command that PXE boots a machine
into Fedora rescue mode (inst.rescue) for live debugging. Auto-clears
after one boot so next reboot returns to normal.

Adds debug state to BastionState, dispatch routing, API endpoints,
labd command routing, and CLI with rescue workflow guide.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bastion/src/labd/src/routes/bastions.ts

@@ -172,6 +172,40 @@ export function registerBastionRoutes(app: FastifyInstance, db: DbClient): void
     }
   });
 
+  // Queue debug/rescue mode — route to correct bastion by MAC
+  app.post<{
+    Body: { mac?: string };
+  }>("/api/machines/debug", async (request, reply) => {
+    const mac = (request.body?.mac ?? "").toLowerCase().replace(/-/g, ":");
+    if (!mac) {
+      return reply.code(400).send({ error: "mac is required" });
+    }
+
+    const bastion = bastionRegistry.findBastionByMac(mac);
+    if (!bastion) {
+      const all = bastionRegistry.getAll();
+      if (all.length === 0) {
+        return reply.code(503).send({ error: "No bastions connected" });
+      }
+      if (all.length === 1) {
+        try {
+          const result = await sendCommand(all[0]!.bastionId, { type: "command-debug", mac });
+          return reply.code(result.status === "ok" ? 200 : 500).send(result);
+        } catch (err) {
+          return reply.code(500).send({ error: err instanceof Error ? err.message : String(err) });
+        }
+      }
+      return reply.code(404).send({ error: `MAC ${mac} not found on any bastion` });
+    }
+
+    try {
+      const result = await sendCommand(bastion.bastionId, { type: "command-debug", mac });
+      return reply.code(result.status === "ok" ? 200 : 500).send(result);
+    } catch (err) {
+      return reply.code(500).send({ error: err instanceof Error ? err.message : String(err) });
+    }
+  });
+
   // Forget machine
   app.delete<{ Params: { mac: string } }>("/api/machines/:mac", async (request, reply) => {
     const mac = request.params.mac.toLowerCase().replace(/-/g, ":");

bastion/src/labd/src/services/bastion-registry.ts

@@ -3,7 +3,7 @@
 
 import { EventEmitter } from "node:events";
 import type { WebSocket } from "ws";
-import type { BastionState, HardwareInfo, InstallConfig, InstalledInfo } from "@lab/shared";
+import type { BastionState, HardwareInfo, InstallConfig, InstalledInfo, DebugConfig } from "@lab/shared";
 
 export interface ConnectedBastion {
   bastionId: string;
@@ -20,6 +20,7 @@ export interface AggregatedState {
   discovered: Record<string, HardwareInfo>;
   install_queue: Record<string, InstallConfig>;
   installed: Record<string, InstalledInfo>;
+  debug: Record<string, DebugConfig>;
 }
 
 export class BastionRegistry extends EventEmitter {
@@ -86,6 +87,7 @@ export class BastionRegistry extends EventEmitter {
       discovered: {},
       install_queue: {},
       installed: {},
+      debug: {},
     };
 
     for (const bastion of this.bastions.values()) {
@@ -98,6 +100,9 @@ export class BastionRegistry extends EventEmitter {
       for (const [mac, info] of Object.entries(bastion.state.installed)) {
         result.installed[mac] = { ...info, bastionId: bastion.bastionId };
       }
+      for (const [mac, dbg] of Object.entries(bastion.state.debug ?? {})) {
+        result.debug[mac] = { ...dbg };
+      }
     }
 
     return result;