docs(org-chart): finalize expanded chart accessibility and usage

Document the shared Vanilla/React Auto API, company selection, styling ownership and preserved card design. Preserve P5-2/P5-3 and P5-4 implementation reports and their historical verification boundaries.

packages/org-chart-react/README.md

@@ -44,8 +44,15 @@ Named runtime export: `OrgChart`. Type exports: `OrgChartProps` and the Core's p
 - Required `dataSource`: the same Core `OrgChartDataSource` interface, `load(options?: { signal?: AbortSignal }): Promise<unknown>`.
 - Required `stylesheetUrls`: `{ engine: string; core: string }`, the exact Core asset contract.
 - Optional `displayMode`: `'interactive'` (default) or `'readOnly'`, passed to the Core composition. Changing it recreates the Core handle.
-- Optional `layoutMode`: `'fixed'` (default) or `'auto'`, independent of `displayMode`. Auto is the P5-1A initial-group preview; automatic recursive layout, collapse and Zoom/Pan remain deferred. Changing it recreates the same Core handle.
-- Optional `companyId`: existing Expanded company preset ID (default `hanmac`). Changing it recreates the handle; Fixed ignores company colors. Unknown Auto IDs report a Core construction lifecycle error. All seven IDs and preview limits are documented in the [Core README](../org-chart/README.md#layout-boundary-p5-1a).
+- Optional `layoutMode`: `'fixed'` (default) or `'auto'`, independent of `displayMode`. Auto renders company forests, collapse and Zoom/Pan/Fit. P5-4 retains the current Expanded card presentation by user decision; external SVG matching is no longer required. Changing mode recreates the Core handle.
+
+See [Expanded usage and styling](../../docs/org-chart/expanded-usage.md) for company
+selection, top nodes, JSON sources, popup ownership and Auto-only CSS examples.
+Keyboard focus reveals offscreen controls at the current Zoom; group-title Hover
+feedback and drag/keyboard activation are implemented in the shared Core.
+- Optional `companyId`: legacy Auto fallback company preset (default `hanmac`). Explicit/inherited organization company identity takes priority; Fixed ignores company colors. Changing it recreates the handle. See [Core README](../org-chart/README.md#layout-boundary-p5-2--p5-3).
+- Optional `selectedCompanyIds`: undefined selects all, [] selects none. Changes call Core selection on the existing instance, preserving per-company collapse state and source counts.
+- Optional `companyTopNodes`, `employeeConnections`, `zoom`: immutable Core configuration maps/range. Identity changes recreate the handle; memoize these objects. Names, positions and profile overrides affect only Auto presentation, not callback data.
 - Optional `organizationLinks`: existing organization-ID-to-URL map, applied only to original 1Depth titles. Missing/blank values retain plain titles. Core validates HTTP(S)/relative URLs and rejects invalid URLs, other schemes and credentials. Treat the map as immutable and memoize it; a new map recreates the handle.
 - Optional `onEmployeeClick(employee, context)`: host-owned information UI, replacing the Core's built-in popup. `context` contains the existing `organization`, `affiliation`, focusable `trigger` card and `originalEvent`. It works in both modes and receives untouched Employee data.
 - Optional `aggregationPolicy`: the Core's `ApprovedAggregationPolicy`.
@@ -79,7 +86,7 @@ Changing callback identity updates the latest committed callback without reload
 
 Cleanup invalidates the wrapper generation, unsubscribes, calls Core's terminal `destroy()` and clears its handle reference. React Strict Mode's setup → cleanup → setup uses a fresh handle. Old generations cannot deliver state/lifecycle callbacks to the new instance; superseded operation rejection handlers are also ignored. Cleanup runs before replacement, leaving at most one active Core per wrapper container. The wrapper does not repeat engine disposal or DOM removal itself.
 
-Core regeneration resets expansion/scroll state according to the existing Core contract. Source errors can recover by replacing the source; Core validation/summary/node behavior remains identical to Vanilla. Invalid runtime Props that prevent Core construction are lifecycle usage errors: fix them and remount the component (for example by changing its React key). No rendered fallback silently replaces an invalid configuration.
+Auto retains valid organization collapse state on source/selection updates, fits reloads/selection and restores toggle focus. Fixed retains its previous regeneration policy. Source errors can recover by replacing the source; Core validation/summary/node behavior remains identical to Vanilla. Invalid runtime Props that prevent Core construction are lifecycle usage errors: fix them and remount the component (for example by changing its React key). No rendered fallback silently replaces an invalid configuration.
 
 Committed callback publication, Core ownership and source updates use layout effects in that order. Cleanup/reload runs synchronously with React commit, so a pending old response cannot notify in a gap before passive cleanup. Server rendering produces only the outer container; SSR/hydration remains outside the verified scope.
 
@@ -94,4 +101,4 @@ npm run typecheck --workspace @hm-design/org-chart-react
 npm run build --workspace @hm-design/org-chart-react
 ```
 
-Storybook is one React host, not proof of every consumer deployment. This adapter does not add pan/zoom, advanced mobile reflow, additional relation overlays or reserved Core presentation sections. SSR/hydration, full screen reader behavior, complete heap/GC recovery, Theme-less rendering, Workdesk reference visual approval and production consumers require their own evidence. Public ESM import without a DOM does not establish SSR/hydration support. Consult the final integration report for the actual typecheck/build/browser/consumer results.
+Storybook is one React host, not proof of every consumer deployment. The adapter delegates Auto Pan/Zoom to Core; it adds no alternate layout, additional relation overlays or API client. SSR/hydration, full screen reader behavior, physical touch, complete heap/GC recovery, Theme-less rendering, Workdesk reference visual approval and production consumers require their own evidence. Public ESM import without a DOM does not establish SSR/hydration support. Consult the final integration report for the actual typecheck/build/browser/consumer results.