feat: add local agent MCP tools and optional source-grounded AI answers

apps/desktop/src/ai-state.ts

@@ -0,0 +1,86 @@
+/** Optional generation is separate from local search and never starts itself. */
+export interface AiConfiguration {
+  enabled: boolean;
+  base_url: string;
+  model: string;
+  api_key: string | null;
+}
+const bytes = (text: string) => new TextEncoder().encode(text).length;
+export function aiConfigurationProblem(config: AiConfiguration): string | null {
+  if (!config.enabled) return "Optional AI is disabled.";
+  let endpoint: URL;
+  try {
+    endpoint = new URL(config.base_url);
+  } catch {
+    return "Enter your OpenAI-compatible endpoint URL.";
+  }
+  if (
+    !["http:", "https:"].includes(endpoint.protocol) ||
+    endpoint.username ||
+    endpoint.password ||
+    endpoint.search ||
+    endpoint.hash ||
+    bytes(config.base_url) > 2048
+  )
+    return "Use an HTTP(S) endpoint without URL credentials, query or fragment.";
+  if (
+    !config.model.trim() ||
+    bytes(config.model) > 200 ||
+    /[\u0000-\u001f\u007f]/u.test(config.model)
+  )
+    return "Enter a model name (up to 200 bytes).";
+  if (
+    config.api_key &&
+    (bytes(config.api_key) > 2048 ||
+      /[\u0000-\u001f\u007f]/u.test(config.api_key))
+  )
+    return "The session API key is invalid or too long.";
+  return null;
+}
+export function aiQuestionProblem(question: string): string | null {
+  return !question.trim()
+    ? "Enter a question about this passage."
+    : bytes(question) > 2048
+      ? "The question exceeds 2048 bytes."
+      : null;
+}
+export function aiEndpointLabel(baseURL: string) {
+  try {
+    return new URL(baseURL).origin;
+  } catch {
+    return "your configured endpoint";
+  }
+}
+export function aiSourceEligible(
+  source?: { kind: string; number: number },
+  media = false,
+) {
+  return (
+    !media &&
+    Boolean(
+      source &&
+        ["page", "paragraph", "line"].includes(source.kind) &&
+        Number.isInteger(source.number) &&
+        source.number > 0,
+    )
+  );
+}
+export class AiRevision {
+  private revision = 0;
+  private selection = "";
+  invalidate() {
+    this.revision++;
+  }
+  select(selection: string) {
+    if (selection !== this.selection) {
+      this.selection = selection;
+      this.invalidate();
+    }
+  }
+  current() {
+    return this.revision;
+  }
+  accepts(revision: number) {
+    return revision === this.revision;
+  }
+}