[refactor] Improve renderer domain organization (#5552)

* [refactor] Improve renderer architecture organization

Building on PR #5388, this refines the renderer domain structure:

**Key improvements:**
- Group all transform utilities in `transform/` subdirectory for better cohesion
- Move canvas state to dedicated `renderer/core/canvas/` domain
- Consolidate coordinate system logic (TransformPane, useTransformState, sync utilities)

**File organization:**
- `renderer/core/canvas/canvasStore.ts` (was `stores/graphStore.ts`)
- `renderer/core/layout/transform/` contains all coordinate system utilities
- Transform sync utilities co-located with core transform logic

This creates clearer domain boundaries and groups related functionality
while building on the foundation established in PR #5388.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Clean up linter-modified files

* Fix import paths and clean up unused imports after rebase

- Update all remaining @/stores/graphStore references to @/renderer/core/canvas/canvasStore
- Remove unused imports from selection toolbox components
- All tests pass, only reka-ui upstream issue remains in typecheck

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* [auto-fix] Apply ESLint and Prettier fixes

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: GitHub Action <action@github.com>

tests-ui/tests/performance/transformPerformance.test.ts

@@ -1,6 +1,6 @@
 import { beforeEach, describe, expect, it } from 'vitest'
 
-import { useTransformState } from '@/renderer/core/layout/useTransformState'
+import { useTransformState } from '@/renderer/core/layout/transform/useTransformState'
 
 // Mock canvas context for testing
 const createMockCanvasContext = () => ({