[Chore] Add Libra review configuration

.libra/instructions.md

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+# EUI review instructions
+
+EUI is a React/Emotion component library consumed by Kibana and other Elastic
+products. Small changes can have a large downstream impact, so weigh
+consumer-facing regressions most heavily. Follow the `wiki/` directory where it
+conflicts with other guidance.
+
+Some guidance in `AGENTS.md` (for example, which contributors may open PRs)
+addresses agents that author changes, not reviewers. Do not flag a PR because of
+who opened it or which issue it references.
+
+## What to prioritize
+
+- Breaking changes to the public API (props, exports, CSS variables, tokens,
+  default values, DOM structure and class names relied on by consumers) that are
+  not called out in the PR's "API Changes" table or changelog.
+- Accessibility regressions: keyboard support, focus management, ARIA
+  roles/labels, and color contrast, in light and dark modes and in high
+  contrast mode (`highContrastMode`).
+- Behavior bugs in shared components (overlays, popovers, flyouts, data grid,
+  form controls) including SSR safety and `ref` / `...rest` prop forwarding.
+- Missing unit tests for changed behavior.
+
+## What to skip
+
+- Formatting; Prettier enforces it. Import order is not enforced anywhere, so do
+  not flag it either.
+- Stylistic preferences not backed by the wiki.
+- Documentation-only wording nits in `packages/website/` and `wiki/` unless
+  the text is factually wrong.
+
+## Conventions to enforce
+
+- Styles use Emotion `*.styles.ts` files with theme tokens (`useEuiTheme`),
+  not hard-coded colors, sizes or SCSS.
+- Changelog entries under `packages/*/changelogs/upcoming/` must describe the
+  consumer-visible change accurately. CI already checks that an entry exists,
+  so do not flag a missing one.

.libra/settings.yaml

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+version: 1
+enabled: true
+
+# EUI PRs are frequently opened as drafts for early feedback; review them on
+# request by adding the bypass label rather than on every push.
+review_drafts: false
+skip_labels:
+  - libra-skip
+draft_bypass_labels:
+  - libra-review-draft
+
+paths:
+  exclude:
+    # Dependencies and lockfiles
+    - "yarn.lock"
+    # Keep .yarn/patches reviewed; they are real changes to dependency code
+    - ".yarn/releases/**"
+    - ".yarn/plugins/**"
+    # Yearly changelogs are collated by the release script
+    - "packages/*/changelogs/CHANGELOG_*.md"
+    # Generated by i18n tooling
+    - "packages/eui/i18ntokens.json"
+    - "packages/eui/i18ntokens_changelog.json"
+    # Jest snapshots are regenerated, review the tests that produce them
+    - "**/__snapshots__/**"
+    # Icon SVG sources and the components generated from them
+    - "packages/eui/src/components/icon/svgs/**"
+    - "packages/eui/src/components/icon/assets/**"
+
+publication:
+  # Drop wording/naming/comment-only notes; they are noise on small, frequent PRs.
+  publish_min_severity: P3
+  block_min_severity: P1
+  verify_min_severity: P1
+  # A flaky specialist should not silence findings from the ones that finished.
+  allow_partial_coverage: true

.libra/specialists/accessibility.md

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+---
+id: accessibility
+description: Reviews keyboard, focus, screen reader and contrast behavior
+apply_to:
+  - "packages/eui/src/components/**/*.ts"
+  - "packages/eui/src/components/**/*.tsx"
+  - "packages/eui/src/services/accessibility/**"
+  - "packages/eui/src/services/focus_trap/**"
+can_block: false
+---
+Check that interactive components remain operable by keyboard, manage and
+restore focus correctly (overlays, popovers, flyouts, modals, menus), expose
+accurate roles, states and accessible names, and do not rely on color alone, including in high contrast mode.
+Verify live-region and `aria-*` usage matches the WAI-ARIA pattern for the
+component. Report only concrete regressions or gaps introduced by the change.

.libra/specialists/docs-and-changelog.md

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+---
+id: docs-and-changelog
+description: Reviews changelog entries, website docs and stories
+apply_to:
+  - "packages/*/changelogs/upcoming/**"
+  - "packages/website/docs/**"
+  - "packages/eui/src/**/*.stories.tsx"
+  - "wiki/**"
+can_block: false
+---
+Changelog entries must describe the consumer-visible effect accurately and use
+`**` subheadings for bug fixes, deprecations and breaking changes, per
+`packages/eui/changelogs/upcoming/_template.md`. Docs and stories should
+reflect new or changed props. Flag factual errors, examples that would not work
+as written, and breaking changes missing from the changelog; do not comment on
+tense, casing or prose style.

.libra/specialists/public-api.md

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+---
+id: public-api
+description: Reviews changes to EUI's public API surface and consumer compatibility
+apply_to:
+  - "packages/eui/src/components/**/*.ts"
+  - "packages/eui/src/components/**/*.tsx"
+  - "packages/eui/src/services/**"
+  - "packages/eui/src/utils/**"
+  - "packages/eui/src/global_styling/**"
+  - "packages/eui/src/index.ts"
+  - "packages/eui-theme-common/src/**"
+  - "packages/eui-theme-borealis/src/**"
+  - "packages/eui-theme-common/package.json"
+  - "packages/eui-theme-borealis/package.json"
+  - "packages/docusaurus-theme/src/**"
+  - "packages/docusaurus-preset/src/**"
+  - "packages/eui/package.json"
+  - "packages/test-helpers/src/**"
+  - "packages/illustrations/src/**"
+  - "packages/eslint-plugin/src/**"
+can_block: true
+---
+Review for breaking changes to what Kibana and other consumers depend on:
+removed or renamed props, exports, tokens, CSS variables, ESLint rules or
+test-helper methods; changed `package.json` exports or peer dependencies; changed defaults;
+narrowed or broadened TypeScript types; changed DOM output or class names;
+props not forwarded (`...rest`, `ref`, `data-test-subj`, `className`).
+A breaking change is acceptable only when the PR documents it, ships a
+changelog entry, and carries the `breaking change` label (required by the wiki;
+it triggers the Kibana due-diligence comment); flag it otherwise. Prefer additive, deprecated-then-removed
+paths over silent behavior changes.

.libra/specialists/styles-theming.md

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+---
+id: styles-theming
+description: Reviews Emotion styles, tokens and theme compatibility
+apply_to:
+  - "**/*.styles.ts"
+  - "**/*.styles.tsx"
+  - "packages/eui/src/global_styling/**"
+  - "packages/eui-theme-borealis/**"
+  - "packages/eui-theme-common/**"
+can_block: false
+---
+Check that styles use theme tokens and EUI mixins/functions instead of
+hard-coded values, work in light and dark color modes, in high contrast mode
+(`highContrastMode`) and in every shipped theme, respect `prefers-reduced-motion`, and keep style generation memoized
+(`useEuiMemoizedStyles`) rather than recomputed each render. Flag SCSS or
+global CSS additions that should be Emotion, and selector or specificity
+changes that could break consumers' overrides.