Fix DashWrapper hydration cache eviction guard on latest-dash

[chgiesse]

Motivation

• Reduce repeated hydration and global layout scans that amplify provider-triggered re-renders by introducing path-scoped caching and indexed layout-hash lookups.
• Address a TypeScript runtime issue encountered when running the renderer test build after integrating recent dash core updates.

Description

• Add a path-scoped hydration cache in dash/dash-renderer/src/wrapper/DashWrapper.tsx with a simple LRU eviction, persistent memoizedKeys, pathKey memoization, and targeted invalidation on forced renders.
• Restructure the layout-hash reducer in dash/dash-renderer/src/reducers/reducer.js to store entries and an index mapping so lookups for affected subpaths are O(1) instead of scanning the whole map.
• Update selector logic in dash/dash-renderer/src/wrapper/selectors.ts to consume the new layoutHashes shape and limit checks to relevant indexed paths only.
• Add a small safety guard around LRU eviction in DashWrapper to avoid calling Map.delete with an undefined key, which fixed the TypeScript compile error surfaced during the test build.

Testing

• Ran npm run private::lint.renderer, which completed successfully.
• Ran cd dash/dash-renderer && npm test -- --runInBand, and the webpack/TypeScript build phase completed (TypeScript error resolved); the Karma browser tests could not execute in this environment because no Chrome binary was available (Please, set "CHROME_BIN" env variable).

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[chatgpt-codex-connector]

Set new-render flag before hydration cache lookup

_newRender is now processed in useEffect, but the render path reads newRender.current before effects run (for example, the cache reuse branch guarded by if (!newRender.current)). When a parent sends _newRender to force a redraw while renderH is unchanged, this render can still return cached hydration, and because mutating a ref in the effect does not schedule another render, the forced redraw may be skipped entirely.

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