Fix typos and outdated docs, make frozen column shadows customizable, and fix the issues found along the way

.vscode/settings.json

@@ -10,7 +10,7 @@
   "editor.formatOnSaveMode": "file",
   "js/ts.experimental.useTsgo": true,
   "js/ts.tsdk.path": "./node_modules/typescript",
-  // ESLint is only used for markdown; JS/TS is linted by the oxc extension
+  // ESLint is only used for Markdown; JS/TS is linted by the Oxc extension
   "eslint.validate": ["markdown"],
   "eslint.problems.shortenToSingleLine": true,
   "files.readonlyInclude": {

AGENTS.md

@@ -9,11 +9,11 @@ src/
   index.ts            # public API surface; all exports go through here
   DataGrid.tsx        # main <DataGrid> component (generic: <R, SR, K>)
   TreeDataGrid.tsx    # wraps DataGrid, adds row grouping (role="treegrid")
-  types.ts            # shared type definitions (e.g. Column, CalculatedColumn, render props, events)
+  types.ts            # shared type definitions (e.g., Column, CalculatedColumn, render props, events)
   hooks/              # shared custom React hooks
-  utils/              # pure utilities (e.g. keyboard, DOM, events, colSpan, style)
+  utils/              # pure utilities (e.g., keyboard, DOM, events, colSpan, style)
   style/              # build-time CSS via ecij tagged templates; layers.css declares @layer order
-  cellRenderers/      # default cell renderers (e.g. checkbox, toggleGroup, value)
+  cellRenderers/      # default cell renderers (e.g., checkbox, toggleGroup, value)
   editors/            # default editors (renderTextEditor)
 test/
   browser/            # vitest browser-mode tests (Playwright: Chromium, Firefox, WebKit)
@@ -30,10 +30,10 @@ website/              # demo site (Vite + TanStack Router)
 - **TypeScript strict** with `exactOptionalPropertyTypes`, `verbatimModuleSyntax`, `erasableSyntaxOnly`. Distinguish missing properties from `undefined` values.
 - **`Maybe<T>`** (`T | undefined | null`) — used for all nullable column/render props. Do not use bare `T | undefined`.
 - **`NoInfer<>`** — wrap callback parameters to prevent reverse type inference into component generics.
-- **CSS layers** — all styles live in nested `@layer rdg.<Name>` sub-layers (e.g. `rdg.Cell`, `rdg.Row`; declared in `src/style/layers.css`). Use `ecij` `css` tagged templates (build-time extraction, not runtime CSS-in-JS). Co-locate styles in component files; `src/style/` is for shared styles.
-- **Dual classnames** — components apply both a semantic class (`rdg-cell`) and a generated hash. Preserve both.
+- **CSS layers** — all styles live in nested `@layer rdg.<Name>` sub-layers (e.g., `rdg.Cell`, `rdg.Row`). When a sub-layer overrides another sub-layer's styles, declare both in `src/style/layers.css`, which sets their order; undeclared sub-layers come after the declared ones. Use `ecij` `css` tagged templates (build-time extraction, not runtime CSS-in-JS). Co-locate styles in component files; `src/style/` is for shared styles.
+- **Dual class names** — components apply both a semantic class (`rdg-cell`) and a generated hash. Preserve both.
 - **Light/dark mode** — handled via CSS `light-dark()` + `color-scheme`, not JS.
-- **Accessibility first** — ARIA attributes (e.g. `aria-colindex`, `aria-rowindex`, `aria-selected`, roles) are required. Tests query by role.
+- **Accessibility first** — ARIA attributes (e.g., `aria-colindex`, `aria-rowindex`, `aria-selected`, roles) are required. Tests query by role.
 - **Build** — `vp pack` bundles the library to `lib/`, then lints the packed package with publint; `ecij` plugin prefixes classes with `rdg-{version}-` (dots→dashes) to avoid cross-version conflicts.
 - **Workflows** — pin every action to a full commit SHA with its version in a comment (Dependabot updates both), pass expressions to `run` steps through `env` instead of inlining `${{ }}`, grant each job only the `permissions` it uses, and check out with `persist-credentials: false`. Jobs that install dependencies only get read permissions: publishing, pushing, and editing PRs happen in separate jobs that receive build output as artifacts and never install the project's dependencies.
 - **Releases** — the header of `.github/workflows/publish.yml` explains how to publish. Its read-only `build` job hands `lib/` to the `publish` job, so the project's dependencies never run with the `id-token: write` permission that npm's trusted publishing relies on, and a separate `release` job creates the GitHub release.
@@ -43,14 +43,14 @@ website/              # demo site (Vite + TanStack Router)
 - Browser tests use `vite-plus/test/browser` + Playwright. `test/setupBrowser.ts` configures `page.render()` via `vitest-browser-react` and registers custom locators via `locators.extend()` — prefer `page.getGrid()`, `page.getCell({ name })`, `page.getRow()`, `page.getHeaderCell()`, `page.getActiveCell()`, etc. over raw `page.getByRole()`.
 - Test helpers in `test/browser/utils.tsx`: `setup()`, `getRowWithCell()`, `getCellsAtRowIndex()`, `validateCellPosition()`, `scrollGrid()`, `safeTab()`, `testCount()`, `testRowCount()`.
 - `test/failOnConsole.ts` fails tests on unexpected console warnings/errors.
-- **Never run visual regression tests** — screenshots are environment-dependent so visual regression tests must run in CI only.
+- **Never run visual regression tests** — screenshots are environment-dependent, so visual regression tests must run in CI only.
 
 ## Tooling
 
 The project uses [Vite+](https://viteplus.dev/guide/), whose global `vp` CLI wraps Vite, Rolldown, Vitest, tsdown, Oxlint, Oxfmt, and Vite Task. Run `vp` directly, not through `npx`. Its docs are in `node_modules/vite-plus/docs`.
 
-- `vp <command>` runs a built-in command, e.g. `vp dev`, `vp check`, `vp test`, `vp pack`, `vp build`.
-- `vp run <task>` runs a task from `vite.config.ts`, e.g. `vp run typecheck`, `vp run eslint`, `vp run ci`.
+- `vp <command>` runs a built-in command, e.g., `vp dev`, `vp check`, `vp test`, `vp pack`, `vp build`.
+- `vp run <task>` runs a task from `vite.config.ts`, e.g., `vp run typecheck`, `vp run eslint`, `vp run ci`.
 - Run `vp install` after pulling changes.
 
 ## Validation
@@ -62,4 +62,4 @@ While iterating, run individual checks instead. The static checks take seconds,
 - `vp run typecheck` type checks with `tsc --build`; `vp check` does not type check.
 - `vp check --fix` formats and lints, fixing what it can. Without `--fix`, a formatting error stops it before linting.
 - `vp run eslint` lints Markdown files.
-- `vp test <files>` runs specific test files, e.g. `vp test test/browser/sorting.test.tsx`. Add `--project "browser (chromium)"` to test in a single browser, or `--project node` to run the SSR test. The full suite takes about a minute.
+- `vp test <files>` runs specific test files, e.g., `vp test test/browser/sorting.test.tsx`. Add `--project "browser (chromium)"` to test in a single browser, or `--project node` to run the SSR test. The full suite takes about a minute.