feat(core): widget polish closure

[RtlZeroMemory]

Summary

Closes remaining widget parity gaps in @rezi-ui/core, adds deterministic test coverage for the changed contracts, and updates widget docs to match the public API.

What changed

• Added slider as a public widget across types, ui factory, renderer/runtime wiring, and docs.
• Added slider behavior coverage (normalization, range/step handling, keyboard routing, render/regression cases).
• Added FocusZone grid navigation integration coverage (navigation: "grid", columns).
• Added deterministic unit tests for toast helper contracts (getToastX/Y, expiration filtering, add/remove/progress updates).
• Added consistent overlay frame styling API (frameStyle) for modal/layer/dropdown/commandPalette/toastContainer.
• Extended modal backdrop config with a backward-compatible object form.
• Added table column overflow policy (clip | ellipsis | middle) and configurable stripe/border styling.
• Updated widget docs (modal, dropdown, layer, layers, command-palette, table, toast) and added slider docs.

Validation

Executed and passed:

• npm run lint
• npm run typecheck
• npm run build
• npm test
• npm run test:e2e
• npm run test:e2e:reduced
• npm run test:native:smoke
• npm -w @rezi-ui/core run build
• npm -w @rezi-ui/core run test
• npm run docs:api
• npm run docs:build
• npm run check:docs

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: c90d5e10c3

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Inset layer content when drawing frame borders

When layer.frameStyle.border is set, the border is drawn and then pushChildrenWithLayout renders the layer content using the full layer rect, so any child that paints edge cells (which is common because layer content is laid out at the same x/y/w/h) will overwrite the border glyphs. This makes the new layer border styling unreliable in normal usage and breaks the expected frame behavior unless every caller manually pads content.

Useful? React with 👍 / 👎.