fix(docs-panel): correct folder nesting by fixing Drizzle camelCase field access

[TYBLHQY]

Problem

In the docs panel, all folders appeared at root level regardless of their parent-child relationships. Subfolders were not nested inside parent folders.

Root Cause

Drizzle ORM with better-sqlite3 returns rows with camelCase property names matching the schema definitions, not the raw SQL snake_case column names:

// schema.ts — Drizzle uses these property names when returning rows
parentId: text(parent_id),
sortOrder: integer(sort_order),

However, folder.store.ts was reading snake_case keys from the returned rows:

// ❌ folder.store.ts — always undefined, defaulting to '' → root level
parentId: f.parent_id,
sortOrder: f.sort_order,

Since f.parent_id was always undefined, every folder was treated as having no parent, so they all appeared at root level in the tree.

Fix

• src/stores/folder.store.ts: Use f.parentId / f.sortOrder (camelCase) in both loadFolders and createFolder, with nullish coalescing defaults
• src/types/ipc.ts: Align FolderRowIPC and DocumentIPCItem interfaces with the actual camelCase keys returned by Drizzle ORM

Verification

• TypeScript compiles clean (npx tsc --noEmit)
• No other snake_case field references remain in the frontend that depend on these types

🤖 Generated with Claude Code