feat(frontend): add TipTap editor and Reasoning panel

Phase 2 implementation:
- Add TipTap editor with bold, italic, headings, lists, code blocks
- Add Reasoning panel with editable reasoning_type, confidence, steps
- Add Markdown to TipTap conversion on document load
- Add PUT /documents/{id}/content endpoint integration
- Add PATCH /documents/{id}/reasoning endpoint integration
- New types: ReasoningStep, ReasoningPanelData, TipTapContentResponse
- New store methods: updateReasoning, addReasoningStep, deleteReasoningStep
- New components: TipTapEditor.vue, ReasoningPanel.vue

src/types/index.ts

@@ -40,17 +40,36 @@ export interface Tag {
   color: string
 }
 
+export interface ReasoningStep {
+  step: number
+  thought: string
+  conclusion: string | null
+}
+
 export interface DocumentReasoning {
-  reasoning_type: 'chain' | 'idea' | 'context' | 'reflection'
+  reasoning_type: 'chain' | 'idea' | 'context' | 'reflection' | null
   confidence: number | null
-  reasoning_steps: Array<{
-    step: number
-    thought: string
-    conclusion: string | null
-  }>
+  reasoning_steps: ReasoningStep[]
   model_source: string | null
 }
 
+export interface ReasoningPanelData {
+  document_id: string
+  has_reasoning: boolean
+  reasoning: DocumentReasoning | null
+  editable: boolean
+}
+
+export interface TipTapContentResponse {
+  content: Record<string, unknown>
+  format: 'tiptap'
+}
+
+export interface ContentUpdateRequest {
+  content: Record<string, unknown>
+  format: 'tiptap' | 'markdown'
+}
+
 export interface Document {
   id: string
   title: string
@@ -60,6 +79,7 @@ export interface Document {
   path: string
   tags: Tag[]
   reasoning: DocumentReasoning | null
+  tiptap_content: Record<string, unknown> | null
   created_at: string
   updated_at: string
 }