fix: address trivial CodeRabbit issues (#9196)

## Summary

Address several trivial CodeRabbit-filed issues: type guard extraction,
ESLint globals, curve editor optimizations, and type relocation.

## Changes

- **What**: Extract `isSingleImage()` type guard in WidgetImageCompare;
add `__DISTRIBUTION__`/`__IS_NIGHTLY__` to ESLint globals and remove
stale disable comments; remove unnecessary `toFixed(4)` from curve path
generation; optimize `histogramToPath` with array join; move
`CurvePoint` type to curve domain

- Fixes #9175
- Fixes #8281
- Fixes #9116
- Fixes #9145
- Fixes #9147

## Review Focus

All changes are mechanical/trivial. Curve path output changes from
fixed-precision to raw floats — SVG handles both fine.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9196-fix-address-trivial-CodeRabbit-issues-3126d73d365081f19a5ce20305403098)
by [Unito](https://www.unito.io)

src/lib/litegraph/src/types/widgets.ts

@@ -1,4 +1,5 @@
 import type { Bounds } from '@/renderer/core/layout/types'
+import type { CurvePoint } from '@/components/curve/types'
 
 import type {
   CanvasColour,
@@ -330,8 +331,6 @@ export interface IBoundingBoxWidget extends IBaseWidget<Bounds, 'boundingbox'> {
   value: Bounds
 }
 
-export type CurvePoint = [x: number, y: number]
-
 export interface ICurveWidget extends IBaseWidget<CurvePoint[], 'curve'> {
   type: 'curve'
   value: CurvePoint[]