Bind sticky notes to windows for per-window layout save/restore

[kordless]

Goal

Tag sticky notes with the windowUid of the Hyperia window that owned them at creation time, so layout save (#82) can capture which stickies were visible per window and restore (#83) can show the right ones.

Current state

Sticky notes (app/sticky.ts:252-264 NoteData) are app-global:

type NoteData = {
  id: string;
  name?: string;
  text?: string;
  color?: string;
  filePath?: string;
  x?: number; y?: number; width?: number; height?: number;
  saved_at?: string;
  last_closed_at?: string;
};

Stickies persist to ~/.hyperia/stickys/notes.json as a flat list. They are not bound to any specific Hyperia window — they float free.

Scope

• Add optional windowUid?: string to NoteData
• When createStickyNote is called from a window context (e.g. via the MCP sticky_note_create tool issued by an agent in a specific window), tag the note with that window's UID
• Add helper listStickiesForWindow(windowUid: string): NoteData[] that returns notes with matching windowUid and no last_closed_at (i.e. visible)
• On layout save (Save window layout on close with modal prompt #82): collect IDs from listStickiesForWindow(windowUid) into SavedLayout.stickyIds
• On layout restore (Restore window layouts on app launch #83): for each stickyIds[i], ensure the note window is open at its saved geometry

Edge cases

• Stickies created before this change have no windowUid — they remain global, not tied to any window
• Closing a sticky removes it from "visible" but not from storage; restore should reopen it
• If a sticky's windowUid window is gone but the user wants to restore the sticky → fall back to the most recently focused window or skip

Files touched

• app/sticky.ts — extend NoteData, add listStickiesForWindow, accept windowUid in createStickyNote
• sidecar/src/ghost/registry.rs and sidecar/src/mcp.rs — when an agent creates a sticky, pass through the originating window UID
• app/ui/window.ts — pass window UID through to sticky creation calls when relevant

Depends on

#82 (which defines the windowUid concept and SavedLayout.stickyIds field). Can be implemented as data-only first, with restore behavior added in #83.