Align @a2ui/react markdown dependency architecture with v0.9 and release @a2ui/react@0.10.2

Once `@a2ui/markdown-it@0.1.0` is released (see #1955), clean up `@a2ui/react`'s package dependency architecture to align with the v0.9 dependency injection model (matching `@a2ui/lit` and `@a2ui/angular`) and release `@a2ui/react@0.10.2`.

### Tasks
1. In `renderers/react/package.json`, move `@a2ui/markdown-it` from `"dependencies"` to optional `"peerDependencies"`:
```json
"peerDependencies": {
"@a2ui/markdown-it": "^0.1.0",
"react": "^19.2.7",
"react-dom": "^19.2.7"
},
"peerDependenciesMeta": {
"@a2ui/markdown-it": {
"optional": true
}
}
```
2. Remove standalone `"markdown-it"` (`^14.2.0`) from `@a2ui/react`'s `"dependencies"` since markdown parsing is handled within `@a2ui/markdown-it`.
3. Bump `@a2ui/react` to `0.10.2` via `./renderers/scripts/increment_version.mjs react 0.10.2`.
4. Run unit and integration tests (`yarn workspace @a2ui/react run test`).
5. Open PR and publish `@a2ui/react@0.10.2`.

Il lavoro si trova nel file `renderers/react/package.json`. Inizia controllando le dependencies e peerDependencies attuali. Usa lo script fornito `./renderers/scripts/increment_version.mjs` per incrementare la versione. Esegui i test con `yarn workspace @a2ui/react run test`. Assicurati che le modifiche siano in linea con il modello di dependency injection utilizzato in `@a2ui/lit` e `@a2ui/angular`.

Scritto dal modello di indicizzazione a partire dal testo della issue.