v0.95.0: enrollment wizards use the raw-device scan /disks/candidates (Impl-2b)

Both wizards now source candidates from the agent's Impl-2a raw-device scan
(GET /disks/candidates, proxied) instead of the Observe-based /api/disks — so a
brand-new non-PVE-storage drive is finally discoverable + enrollable end-to-end.
agentapi.ListCandidates + a passthrough proxy (no controller-side filtering; the
agent's unclaimed filter is authoritative). storage_init renders `initialize`,
storage_attach renders `attach`; the enroll flow + Impl-1 guarded mkfs unchanged.
Tests + go build/vet/test clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

controller/internal/agentapi/client.go

@@ -347,6 +347,40 @@ func (c *Client) Disks(ctx context.Context) (DisksResponse, error) {
 	return out, nil
 }
 
+// DiskCandidate mirrors one entry from the agent's GET /disks/candidates (Impl-2a candidates.go) —
+// a host disk the agent's unclaimed-disk filter proved is FREE for Felhom to enroll.
+type DiskCandidate struct {
+	Device      string `json:"device"`
+	SizeBytes   int64  `json:"size_bytes"`
+	Model       string `json:"model,omitempty"`
+	FSType      string `json:"fstype,omitempty"`
+	DataBearing bool   `json:"data_bearing"`
+	Mountable   bool   `json:"mountable"`
+	MountSource string `json:"mount_source,omitempty"`
+	DurableID   string `json:"durable_id,omitempty"`
+}
+
+// CandidatesResult mirrors GET /disks/candidates: disks free to enroll, split into initialize (all
+// unclaimed) and attach (the mountable-FS subset).
+type CandidatesResult struct {
+	VMID       int             `json:"vmid"`
+	Initialize []DiskCandidate `json:"initialize"`
+	Attach     []DiskCandidate `json:"attach"`
+}
+
+// ListCandidates fetches the host disks free for Felhom to enroll (Impl-2b wizard source).
+func (c *Client) ListCandidates(ctx context.Context) (CandidatesResult, error) {
+	var out CandidatesResult
+	body, err := c.get(ctx, "/disks/candidates")
+	if err != nil {
+		return out, err
+	}
+	if err := json.Unmarshal(body, &out); err != nil {
+		return out, fmt.Errorf("agentapi: decode /disks/candidates: %w", err)
+	}
+	return out, nil
+}
+
 // AssignDisk attaches a drive (by fs-UUID) as a host mount (benign, self-serve).
 func (c *Client) AssignDisk(ctx context.Context, uuid, where, fstype, options string) error {
 	_, err := c.post(ctx, "/disks/assign", map[string]string{