feat(31-01): define WorkflowProposal types for reviewable workflow structure

Add types for the workflow proposal system:
- ProposedNode: node with purpose, title, and suggested settings
- ProposedConnection: connection with human-readable description
- ProposedGroup: optional grouping with purpose description
- WorkflowProposal: complete reviewable workflow structure

These types enable the LLM to propose workflow structure before
generating full workflow JSON, allowing user review and editing.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/types/quickstart.ts

@@ -1,3 +1,5 @@
+import type { NodeType } from "./nodes";
+
 export type QuickstartView = "initial" | "templates" | "vibe";
 
 export type TemplateCategory = "simple" | "advanced" | "community";
@@ -22,3 +24,81 @@ export interface CommunityWorkflowMeta {
   hoverImage?: string;
   sortOrder?: number;
 }
+
+// ============================================================================
+// Workflow Proposal Types
+// ============================================================================
+
+/**
+ * A proposed node in the workflow - describes purpose and configuration
+ * without internal state or positioning details
+ */
+export interface ProposedNode {
+  /** Temporary ID like "node-1" */
+  id: string;
+  /** Node type: imageInput, prompt, nanoBanana, etc. */
+  type: NodeType;
+  /** Human-readable description of this node's role */
+  purpose: string;
+  /** customTitle for the node */
+  suggestedTitle: string;
+  /** For prompt nodes: the suggested prompt text */
+  suggestedPrompt?: string;
+  /** For nanoBanana/generateVideo: the suggested model */
+  suggestedModel?: string;
+  /** For nanoBanana/generateVideo: suggested settings like aspectRatio */
+  suggestedSettings?: Record<string, unknown>;
+}
+
+/**
+ * A proposed connection between nodes - describes data flow
+ */
+export interface ProposedConnection {
+  /** Source node ID */
+  from: string;
+  /** Target node ID */
+  to: string;
+  /** Connection type */
+  type: "image" | "text" | "reference";
+  /** Human-readable description of data flow */
+  description: string;
+}
+
+/**
+ * A proposed group for organizing related nodes
+ */
+export interface ProposedGroup {
+  /** Group name */
+  name: string;
+  /** Group color */
+  color: "neutral" | "blue" | "green" | "purple" | "orange";
+  /** IDs of nodes in this group */
+  nodeIds: string[];
+  /** Human-readable description of what this group represents */
+  purpose: string;
+}
+
+/**
+ * Workflow complexity estimate
+ */
+export type WorkflowComplexity = "simple" | "moderate" | "complex";
+
+/**
+ * A complete workflow proposal - reviewable structure before JSON generation
+ */
+export interface WorkflowProposal {
+  /** Workflow name */
+  name: string;
+  /** One-paragraph summary of what workflow does */
+  description: string;
+  /** Proposed nodes */
+  nodes: ProposedNode[];
+  /** Proposed connections */
+  connections: ProposedConnection[];
+  /** Optional groups for organizing nodes */
+  groups?: ProposedGroup[];
+  /** Estimated complexity */
+  estimatedComplexity: WorkflowComplexity;
+  /** Any caveats or limitations */
+  warnings?: string[];
+}