fix(app): preserve IME composition across text fields (#3517)

* fix(app): preserve IME composition in form inputs

Form model publication was replaying changing default text into the native or DOM editing surface. Keep the editing surface authoritative, defer web publication until composition commits, and reserve resetKey changes for explicit text replacement.

* refactor(app): centralize text editing authority

Route every app text field, including the composer and plugin runtime, through one platform-owned editing primitive. Its type and runtime reject controlled value replay, its command handle owns programmatic replacement, and lint prevents raw React Native TextInput imports outside the boundary.

* fix(app): restore composer placeholder styling

packages/app/src/plugins/evaluate.ts

@@ -1,5 +1,6 @@
 import * as React from "react";
 import * as ReactJsxRuntime from "react/jsx-runtime";
+// eslint-disable-next-line no-restricted-imports -- the plugin runtime replaces raw TextInput with Paseo's editing primitive below.
 import * as ReactNative from "react-native";
 // eslint-disable-next-line no-restricted-imports -- plugin bundles receive TanStack's real runtime, not Paseo's query wrappers.
 import * as ReactQuery from "@tanstack/react-query";
@@ -21,6 +22,9 @@ import { createPluginContext, type PluginRegistrationCollector } from "@paseo/pl
 import type { EvaluatedPlugin } from "./types";
 import type { ComponentType } from "react";
 import { resolvePluginIcon } from "./icons";
+import { EditingTextInput } from "@/components/ui/text-input";
+
+const PluginReactNative = { ...ReactNative, TextInput: EditingTextInput };
 
 const CONTRIBUTION_ID = /^[a-z][a-z0-9-]*$/;
 
@@ -147,7 +151,7 @@ export function evaluatePluginClientBundle(id: string, bundle: string): Evaluate
   const runtimeRequire = (name: string): unknown => {
     if (name === "react") return React;
     if (name === "react/jsx-runtime") return ReactJsxRuntime;
-    if (name === "react-native") return ReactNative;
+    if (name === "react-native") return PluginReactNative;
     if (name === "@paseo/plugin") {
       return {
         defineAttachmentSource,