Chiseling at #31590 and bringing what's atomically committable out of there.

This simply adds eslint checks to pre-commit. Note that:
- it requires having run `npm i` in superset-frontend
- it's set up to NOT run in CI as part of the pre-commit validation workflow, since we run eslint more formally in another workflow

Why doing this? Currently it's common to forget to run `npm run lint` prior to committing/pushing, so people can waste time waiting for CI to fail where it could be caught easily. It's nice to have pre-commit do the check itself because it will only evaluate the files that have changed, making it much faster than running a full lint run against all files.

…rt/e2e.ts

While working on #31590, I noticed that `expect` was not properly imported. It was using it from global for some unknown reason.

Chiseling at #31590 that has gotten big / unruly, in this PR is a refactor of Alert-related components, going vanilla AntD.

Also. Deprecating colors.alerts since it's ambiguous/redundant with warning/error and does not exist in antd-v5

Chiseling at #31590 that has gotten big / unruly, in this PR is a refactor of Alert-related components, going vanilla AntD.

Also. Deprecating colors.alerts since it's ambiguous/redundant with warning/error and does not exist in antd-v5

Chiseling at #31590 that has gotten big / unruly, in this PR is a refactor of Alert-related components, going vanilla AntD.

Also. Deprecating colors.alerts since it's ambiguous/redundant with warning/error and does not exist in antd-v5

Chiseling at #31590 that has gotten big / unruly, in this PR is a refactor of Alert-related components, going vanilla AntD.

Also. Deprecating colors.alerts since it's ambiguous/redundant with warning/error and does not exist in antd-v5

Chiseling at #31590 that has gotten big / unruly, in this PR is a refactor of Alert-related components, going vanilla AntD.

Also. Deprecating colors.alerts since it's ambiguous/redundant with warning/error and does not exist in antd-v5

The APP_ICON configuration variable was deprecated in PR #31590 (Ant Design v5 theming overhaul) but this breaking change was not documented in UPDATING.md. Users were confused when their custom logos stopped working in Superset 6.0.0rc1.

Added clear migration instructions showing how to replace APP_ICON with the new THEME_DEFAULT.token.brandLogoUrl configuration.

Resolves misconceptions about APP_ICON functionality mentioned in issue #34824.

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

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

Table chart column headers were rendering with `id="header-undefined"`
instead of meaningful IDs, breaking CSS customization and ARIA
accessibility.

**Root Cause:**
PR #31590 (Ant Design v5) changed header IDs from `column.key` to
`column.originalLabel`, but `originalLabel` is only set for time-comparison
columns (added in PR #32665), leaving regular columns with undefined values.

**Solution:**
Implemented defensive fallback with sanitization:
- Headers: `id="header-${sanitizeHeaderId(column.originalLabel || column.key)}"`
- Cells: `aria-labelledby="header-${sanitizeHeaderId(column.originalLabel || column.key)}"`

**Sanitization Required:**
Column identifiers can contain CSS-unsafe characters (%, #, △, spaces),
so added sanitization function to ensure valid CSS selectors and ARIA
references.

**Changes:**
- Added `sanitizeHeaderId()` helper function
- Updated header `id` attribute with fallback + sanitization
- Updated cell `aria-labelledby` with fallback + sanitization
- Added 2 comprehensive tests (regular + time-comparison columns)
- Fixed test fixture mutation issue

**Tests verify:**
- No "undefined" in any header IDs
- All IDs are CSS-safe (no spaces or special characters)
- All ARIA relationships valid (cells reference existing headers)
- Works for both regular and time-comparison columns

Fixes #35783

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

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

The APP_ICON configuration variable was deprecated in PR #31590 (Ant Design v5 theming overhaul) but this breaking change was not documented in UPDATING.md. Users were confused when their custom logos stopped working in Superset 6.0.0rc1.

Added clear migration instructions showing how to replace APP_ICON with the new THEME_DEFAULT.token.brandLogoUrl configuration.

Resolves misconceptions about APP_ICON functionality mentioned in issue #34824.

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

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