admin(machines): fix machine detail not loading by switching to server-side fetch by ID

- Add Convex query machines.getById with full payload (metrics/inventory)
- Update AdminMachineDetailsClient to use getById instead of listByTenant+find
- Update MachineBreadcrumbs to fetch hostname by ID

This prevents the empty state when the list query hasn’t loaded or filtered out the machine.

convex/machines.ts

@@ -850,6 +850,118 @@ export const listByTenant = query({
   },
 })
 
+export const getById = query({
+  args: {
+    id: v.id("machines"),
+    includeMetadata: v.optional(v.boolean()),
+  },
+  handler: async (ctx, args) => {
+    const includeMetadata = Boolean(args.includeMetadata)
+    const now = Date.now()
+
+    const machine = await ctx.db.get(args.id)
+    if (!machine) return null
+
+    const tokens = await ctx.db
+      .query("machineTokens")
+      .withIndex("by_machine", (q) => q.eq("machineId", machine._id))
+      .collect()
+
+    const activeToken = tokens.find((token) => !token.revoked && token.expiresAt > now) ?? null
+
+    const offlineThresholdMs = getOfflineThresholdMs()
+    const staleThresholdMs = getStaleThresholdMs(offlineThresholdMs)
+    const manualStatus = (machine.status ?? "").toLowerCase()
+    let derivedStatus: string
+    if (machine.isActive === false) {
+      derivedStatus = "deactivated"
+    } else if (["maintenance", "blocked"].includes(manualStatus)) {
+      derivedStatus = manualStatus
+    } else if (machine.lastHeartbeatAt) {
+      const age = now - machine.lastHeartbeatAt
+      if (age <= offlineThresholdMs) {
+        derivedStatus = "online"
+      } else if (age <= staleThresholdMs) {
+        derivedStatus = "offline"
+      } else {
+        derivedStatus = "stale"
+      }
+    } else {
+      derivedStatus = machine.status ?? "unknown"
+    }
+
+    const meta = includeMetadata ? (machine.metadata ?? null) : null
+    let metrics: Record<string, unknown> | null = null
+    let inventory: Record<string, unknown> | null = null
+    let postureAlerts: Array<Record<string, unknown>> | null = null
+    let lastPostureAt: number | null = null
+    if (meta && typeof meta === "object") {
+      const metaRecord = meta as Record<string, unknown>
+      if (metaRecord.metrics && typeof metaRecord.metrics === "object") {
+        metrics = metaRecord.metrics as Record<string, unknown>
+      }
+      if (metaRecord.inventory && typeof metaRecord.inventory === "object") {
+        inventory = metaRecord.inventory as Record<string, unknown>
+      }
+      if (Array.isArray(metaRecord.postureAlerts)) {
+        postureAlerts = metaRecord.postureAlerts as Array<Record<string, unknown>>
+      }
+      if (typeof metaRecord.lastPostureAt === "number") {
+        lastPostureAt = metaRecord.lastPostureAt as number
+      }
+    }
+
+    const linkedUserIds = machine.linkedUserIds ?? []
+    const linkedUsers = await Promise.all(
+      linkedUserIds.map(async (id) => {
+        const u = await ctx.db.get(id)
+        if (!u) return null
+        return { id: u._id, email: u.email, name: u.name }
+      })
+    ).then((arr) => arr.filter(Boolean) as Array<{ id: string; email: string; name: string }>)
+
+    return {
+      id: machine._id,
+      tenantId: machine.tenantId,
+      hostname: machine.hostname,
+      companyId: machine.companyId ?? null,
+      companySlug: machine.companySlug ?? null,
+      osName: machine.osName,
+      osVersion: machine.osVersion ?? null,
+      architecture: machine.architecture ?? null,
+      macAddresses: machine.macAddresses,
+      serialNumbers: machine.serialNumbers,
+      authUserId: machine.authUserId ?? null,
+      authEmail: machine.authEmail ?? null,
+      persona: machine.persona ?? null,
+      assignedUserId: machine.assignedUserId ?? null,
+      assignedUserEmail: machine.assignedUserEmail ?? null,
+      assignedUserName: machine.assignedUserName ?? null,
+      assignedUserRole: machine.assignedUserRole ?? null,
+      linkedUsers,
+      status: derivedStatus,
+      isActive: machine.isActive ?? true,
+      lastHeartbeatAt: machine.lastHeartbeatAt ?? null,
+      heartbeatAgeMs: machine.lastHeartbeatAt ? now - machine.lastHeartbeatAt : null,
+      registeredBy: machine.registeredBy ?? null,
+      createdAt: machine.createdAt,
+      updatedAt: machine.updatedAt,
+      token: activeToken
+        ? {
+            expiresAt: activeToken.expiresAt,
+            lastUsedAt: activeToken.lastUsedAt ?? null,
+            usageCount: activeToken.usageCount ?? 0,
+          }
+        : null,
+      metrics,
+      inventory,
+      postureAlerts,
+      lastPostureAt,
+      remoteAccess: machine.remoteAccess ?? null,
+    }
+  },
+})
+
 export const listAlerts = query({
   args: {
     machineId: v.id("machines"),