feat(web): add language model inputModalities capability plumbing

Add an optional `inputModalities` declaration to language model config and
expose a resolved capability set to the client.

- Schema: add optional `inputModalities` (`text` | `image` | `pdf`) to every
  provider definition in `schemas/v3/languageModel.json` and regenerate the
  schema types/snippets.
- Add a fail-closed `resolveModelInputModalities` resolver that defaults to
  text-only when a model does not declare its input modalities.
- Expose the resolved `inputModalities` on the client-safe `LanguageModelInfo`
  (populated via `getConfiguredLanguageModelsInfo` and the MCP ask path).

This is groundwork for chat file attachments. It adds no attachment UI and no
live provider capability probing yet.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: whoisthey

docs/snippets/schemas/v3/index.schema.mdx

@@ -762,6 +762,10 @@ export interface AmazonBedrockLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 /**
  * Optional headers to use with the model.
@@ -842,6 +846,10 @@ export interface AnthropicLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface AzureLanguageModel {
   /**
@@ -897,6 +905,10 @@ export interface AzureLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface DeepSeekLanguageModel {
   /**
@@ -936,6 +948,10 @@ export interface DeepSeekLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface GoogleGenerativeAILanguageModel {
   /**
@@ -983,6 +999,10 @@ export interface GoogleGenerativeAILanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface GoogleVertexAnthropicLanguageModel {
   /**
@@ -1030,6 +1050,10 @@ export interface GoogleVertexAnthropicLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface GoogleVertexLanguageModel {
   /**
@@ -1085,6 +1109,10 @@ export interface GoogleVertexLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface MistralLanguageModel {
   /**
@@ -1124,6 +1152,10 @@ export interface MistralLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface OpenAILanguageModel {
   /**
@@ -1171,6 +1203,10 @@ export interface OpenAILanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface OpenAICompatibleLanguageModel {
   /**
@@ -1215,6 +1251,10 @@ export interface OpenAICompatibleLanguageModel {
    * Optional temperature setting to use with the model.
    */
   temperature?: number;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 /**
  * Optional query parameters to include in the request url.
@@ -1279,6 +1319,10 @@ export interface OpenRouterLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface XaiLanguageModel {
   /**
@@ -1318,6 +1362,10 @@ export interface XaiLanguageModel {
    */
   temperature?: number;
   headers?: LanguageModelHeaders;
+  /**
+   * Optional list of input modalities this model can accept. Used to gate non-text chat attachments. When omitted, the model is treated as text-only (fail-closed).
+   */
+  inputModalities?: ("text" | "image" | "pdf")[];
 }
 export interface GitHubAppConfig {
   /**