feat(coding): add PI-105 product file host API

tests/electron-runtime/coding-files-host.test.ts

@@ -0,0 +1,41 @@
+import { mkdtemp, rm, writeFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+import { afterEach, describe, expect, it } from 'vitest';
+import type { CodingProductHost } from '../../electron/api/coding-product-services';
+import type { HostApiContext } from '../../electron/api/context';
+import { dispatchHostApiRequest } from '../../electron/api/host-api-dispatcher';
+import { CodingProjectFileService } from '../../electron/coding-projects/project-files';
+
+const roots: string[] = [];
+
+afterEach(async () => {
+  await Promise.all(roots.splice(0).map((root) => rm(root, { recursive: true, force: true })));
+});
+
+describe('PI-105 Electron Host API seam', () => {
+  it('reads a project-relative file through the Main dispatcher without loopback or path leakage', async () => {
+    const root = await mkdtemp(path.join(tmpdir(), 'makelore-pi-host-dispatch-'));
+    roots.push(root);
+    await writeFile(path.join(root, 'notes.txt'), 'Main-owned content\n', 'utf8');
+    const files = new CodingProjectFileService();
+    const host = {
+      fileContent: async (filePath: string) => await files.content(root, filePath),
+    } as CodingProductHost;
+    const ctx = {
+      codingProducts: { host, attachments: {}, productTools: {} },
+    } as HostApiContext;
+
+    const response = await dispatchHostApiRequest(ctx, {
+      path: '/api/coding/files/content?path=notes.txt',
+    });
+    expect(response).toMatchObject({
+      status: 200,
+      ok: true,
+      json: {
+        file: { path: 'notes.txt', content: 'Main-owned content\n', truncated: false },
+      },
+    });
+    expect(JSON.stringify(response.json)).not.toContain(root);
+  });
+});