feat(apps): stepped creation wizard, branch previews, and app-creation fixes

This session (frontend focus):
- Rebuild /apps/new as a 4-step wizard (Basics → Configure → Trigger → Review):
  WizardRail, SourceKindPicker card grid, AppManifest review, per-step validation,
  ConfirmDialog-based unsaved-changes guard.
- Extract lib/workload/sourceForms.ts (single source of truth for source_config)
  + {Image,Compose,Static,Dockerfile}SourceForm + StaticDiscoveryWizard; fold the
  /apps/[id] edit form onto the same components (removes the duplication). Add
  vitest + sourceForms unit tests.
- Branch preview environments UI: /chain is_preview/preview_branch + a Preview
  environments panel on /apps/[id] (per-branch URLs, ConfirmDialog teardown, armed
  state); RegistryImagePicker on the registry trigger and the image source.
- Fixes: image-inspect 404 -> admin-gated POST /api/discovery/image/inspect;
  conflict-panel blur flicker; friendly localized discovery errors; CPU/Memory
  label hints; dashboard + /apps "Total workloads" count only source_kind workloads
  (drop stale trigger_kind gate); NPM cert/access-list name cache; EntityPicker
  empty-list guard.
- Update CLAUDE.md frontend conventions + add a Build & Test section.

Also captures pre-existing in-progress platform work (not from this session):
workload notifications, Prometheus metrics export, store lockfile, health probes,
backup hardening, and related store/webhook/scheduler changes.

internal/api/workload_chain.go

@@ -13,18 +13,29 @@ import (
 	"github.com/alexei/tinyforge/internal/auth"
 	"github.com/alexei/tinyforge/internal/store"
 	"github.com/alexei/tinyforge/internal/workload/plugin"
+	"github.com/alexei/tinyforge/internal/workload/preview"
 )
 
 // chainNode is the lightweight shape returned by /chain — we deliberately
 // don't return full plugin.Workload values for ancestor/descendant rows
 // because the secret fields don't belong in a chain-traversal response.
+//
+// IsPreview / PreviewBranch surface branch-preview children to the UI so it
+// can render them in a dedicated "Preview environments" panel rather than as
+// undistinguished stage children. They are computed against the chain's
+// `self` workload via preview.IsPreviewChild — the canonical "this child is a
+// branch preview" test that reverses the MaterializeForBranch naming formula.
+// Both are zero-valued (false / "") for the parent and self nodes and for
+// operator-created stage children.
 type chainNode struct {
-	ID         string `json:"id"`
-	Name       string `json:"name"`
-	SourceKind string `json:"source_kind"`
-	TriggerKind string `json:"trigger_kind"`
-	CreatedAt  string `json:"created_at"`
-	UpdatedAt  string `json:"updated_at"`
+	ID            string `json:"id"`
+	Name          string `json:"name"`
+	SourceKind    string `json:"source_kind"`
+	TriggerKind   string `json:"trigger_kind"`
+	IsPreview     bool   `json:"is_preview"`
+	PreviewBranch string `json:"preview_branch,omitempty"`
+	CreatedAt     string `json:"created_at"`
+	UpdatedAt     string `json:"updated_at"`
 }
 
 func chainNodeOf(w store.Workload) chainNode {
@@ -38,6 +49,32 @@ func chainNodeOf(w store.Workload) chainNode {
 	}
 }
 
+// previewBranchOf extracts the branch a preview child was materialized for
+// from its source_config (the `branch` key MaterializeForBranch wrote).
+// Returns "" on a missing/malformed config — the caller only calls this for
+// rows preview.IsPreviewChild already confirmed, so a blank result just means
+// the JSON couldn't be decoded.
+func previewBranchOf(w store.Workload) string {
+	var cfg struct {
+		Branch string `json:"branch"`
+	}
+	if w.SourceConfig != "" {
+		_ = json.Unmarshal([]byte(w.SourceConfig), &cfg)
+	}
+	return cfg.Branch
+}
+
+// childChainNode builds a chainNode for a child row, marking it as a branch
+// preview (and attaching its branch) when it was materialized from `self`.
+func childChainNode(self, child store.Workload) chainNode {
+	node := chainNodeOf(child)
+	if preview.IsPreviewChild(self, child) {
+		node.IsPreview = true
+		node.PreviewBranch = previewBranchOf(child)
+	}
+	return node
+}
+
 // getWorkloadChain handles GET /api/workloads/{id}/chain.
 //
 // Returns the workload's parent (or nil), itself, and its direct children
@@ -76,7 +113,7 @@ func (s *Server) getWorkloadChain(w http.ResponseWriter, r *http.Request) {
 	}
 	children := make([]chainNode, 0, len(childRows))
 	for _, c := range childRows {
-		children = append(children, chainNodeOf(c))
+		children = append(children, childChainNode(self, c))
 	}
 
 	respondJSON(w, http.StatusOK, map[string]any{