fix: keep notifications and recovery UI above deep modal stacks (#3095)

[JuliaMV]

Summary

• Fixes #3095: with many stacked layers (e.g. large grids of tooltips/buttons), modal z-index could exceed the old fixed snackbar value (100500), so notifications appeared behind the modal.
• Snackbar / notification host stacking now follows uuiLayout.getTopOverlayZIndex(), keeping the previous value as a minimum so existing apps do not regress.
• LayoutContext exposes a stable top-overlay index based on registered layers; ErrorHandler recovery ModalBlocker uses the same source instead of a hardcoded z-index.

Issue link:

3095

[github-actions]

Generated by: track-bundle-size
Generated at: Fri, 15 May 2026 12:17:08 GMT
Bundle size diff (in kBytes). Not gzipped. Both CSS & JS included.
Baseline: v6.3.1 (2025-12-03)
CI Status: ok

Module	Baseline Size (v6.3.1)	Size	Diff	Within Threshold	Threshold (min - max)
templateApp	693.09	699.98	+6.89 js:+4.96 css:+1.93	🆗	623.78 - 762.39
@epam/app	5586.96	5526.92	-60.04 js:-60.41 css:+0.37	🆗	5028.26 - 6145.65
@epam/electric	5.04	5.04	0 js:0 css:0	🆗	4.53 - 5.54
@epam/promo	55.61	55.57	-0.05 js:0 css:-0.05	🆗	50.05 - 61.17
@epam/uui-extra	0.21	0.21	0 js:0 css:0	🆗	0.19 - 0.23
@epam/loveship	92.81	96.24	+3.43 js:+3.48 css:-0.05	🆗	83.53 - 102.09
@epam/uui-components	257.49	261.27	+3.77 js:+2.25 css:+1.52	🆗	231.75 - 283.25
@epam/uui-core	324.75	329.55	+4.8 js:+4.8 css:0	🆗	292.27 - 357.23
@epam/uui-db	41.63	41.72	+0.08 js:+0.08 css:0	🆗	37.47 - 45.8
@epam/uui-docs	181.03	194.73	+13.71 js:+13.71 css:0	🆗	162.92 - 199.13
@epam/uui-editor	174.1	173.28	-0.82 js:-0.82 css:+0	🆗	156.69 - 191.51
@epam/uui-timeline	75.5	75.49	-0.01 js:0 css:0	🆗	67.95 - 83.05
@epam/uui	527.51	548.47	+20.96 js:+4.3 css:+16.66	🆗	474.76 - 580.26

new sizes (raw)

To set the sizes as a new baseline, you can copy/paste next content to the uui-build/config/bundleSizeBaseLine.json and commit the file.

{
  "version": "6.4.4",
  "timestamp": "2026-05-15",
  "sizes": {
    "templateApp": {
      "css": 259446,
      "js": 457328
    },
    "@epam/app": {
      "css": 720897,
      "js": 4938667
    },
    "@epam/electric": {
      "css": 2275,
      "js": 2883
    },
    "@epam/promo": {
      "css": 47756,
      "js": 9145
    },
    "@epam/uui-extra": {
      "css": 0,
      "js": 213
    },
    "@epam/loveship": {
      "css": 55330,
      "js": 43218
    },
    "@epam/uui-components": {
      "css": 25157,
      "js": 242379
    },
    "@epam/uui-core": {
      "css": 0,
      "js": 337461
    },
    "@epam/uui-db": {
      "css": 0,
      "js": 42718
    },
    "@epam/uui-docs": {
      "css": 2152,
      "js": 197255
    },
    "@epam/uui-editor": {
      "css": 12954,
      "js": 164486
    },
    "@epam/uui-timeline": {
      "css": 2199,
      "js": 75104
    },
    "@epam/uui": {
      "css": 215800,
      "js": 345831
    }
  }
}

---

Generated by: generate-components-api
CI Status: error

Total amount of exported types/props without JSDoc comments

	Amount
Types	338 (+0) 🆗
Props	221 (+1) ⛔

New missing comments

NOTE: It's either a new exported types/props without JSDoc, or it's an existing code from which you deleted the JSDoc comments.

Types:
- <empty>
Props:
- @epam/uui-components:SnackbarProps/zIndex

[i-runets]

I think we can skip this check for rawStyles type and just do this:

const rootStyle = rawStyle || this.props.zIndex !== undefined
    ? {
        ...(rawStyle ?? {}),
        ...(this.props.zIndex !== undefined ? { zIndex: this.props.zIndex } : {}),
    }
    : undefined;

rawStyle is already typed as React.CSSProperties(inherits from IHasRawProps<React.HTMLAttributes<HTMLDivElement>>), and from what I can see, UUI rarely does this kind of check.