Infinite Canvas — Phase 4: Notes, Drawing, File manager + Editor

[Legacynnn]

Part of the Infinite Canvas epic: #61

Phase 4 — More panels: Notes, Drawing, File manager + Editor

Add the productivity panel types beyond conversation/terminal.

Scope

• Notes panel — markdown / rich-text note surface; content persisted in canvas_panels.config (or a dedicated table if size warrants). Reuse existing markdown rendering (streamdown/Lexical) where sensible.
• Drawing / whiteboard panel — tldraw-native drawing primitives; persisted with the canvas.
• File manager panel — file-tree browser scoped to a working directory.
• Editor panel — Monaco file editing (reuse src/features/editor/ + monaco-runtime.ts), scoped to a panel's working dir; open files from the file-manager panel or from a connected panel's context.
• All new DOM panels participate in the (Phase 5) translucency slider.

Out of scope

Browser/app preview (Phase 7), global controls (Phase 5), CLI (Phase 6).

Acceptance

• Notes, drawing, file-manager, and editor panels are creatable, functional, resizable, and persist across restart.
• Editing a file through the editor panel writes to disk correctly and reflects in the workspace.
• Persistence changes covered by tests; lint/typecheck/test pass.