feat(FN-3195): document llama.cpp provider setup and onboarding

Docs(FN-3195): adds llama.cpp provider setup and onboarding documentation to the main and dashboard READMEs.

Fusion-Task-Id: FN-3195

packages/pi-llama-cpp/index.ts

@@ -0,0 +1,38 @@
+import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
+import {
+  DEFAULT_CONTEXT_WINDOW,
+  DEFAULT_MAX_TOKENS,
+  PROVIDER_ID,
+  PROVIDER_NAME,
+} from "./src/constants.js";
+import { resolveLlamaServerApiKey, resolveLlamaServerUrl } from "./src/resolver.js";
+import { isLlamaServerReady, listLlamaModels } from "./src/retriever.js";
+
+export default async function (pi: ExtensionAPI): Promise<void> {
+  const cwd = process.cwd();
+  if (!(await isLlamaServerReady(cwd))) {
+    return;
+  }
+
+  const [url, models, apiKey] = await Promise.all([
+    resolveLlamaServerUrl(cwd),
+    listLlamaModels(cwd),
+    resolveLlamaServerApiKey(),
+  ]);
+
+  pi.registerProvider(PROVIDER_ID, {
+    name: PROVIDER_NAME,
+    baseUrl: `${url}/v1`,
+    api: "openai-completions",
+    apiKey: apiKey ?? "",
+    models: models.map((model) => ({
+      id: model.id,
+      name: model.id,
+      reasoning: true,
+      input: ["text", "image"] as Array<"text" | "image">,
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: DEFAULT_CONTEXT_WINDOW,
+      maxTokens: DEFAULT_MAX_TOKENS,
+    })),
+  });
+}