feat: add a tool catalog and local MCP server

Define tools that answer questions from the app's data once, independent
of the surface that exposes them. A tool declares its arguments and the
services it reads; applications compose tools with their own services and
optional call interceptors. Queries reuse the layers' portable source
factories, so they run wherever an application routes /api requests.

The first queries are get_earthquakes, get_active_fires and
get_recent_launches, with a shared area argument (place name, bounding
box, or point and radius) and capped lists.

gods-eye-view/tools/mcp adapts a catalog to the Model Context Protocol
with a small JSON-RPC handler and a stateless HTTP transport, adding no
dependencies. npm run mcp serves Core's tools over stdio to local clients
such as Claude Code, reading from a running app. Both exports are
portable and checked by check:boundaries; the app does not import them.

src/tools/localServer.test.mjs

@@ -0,0 +1,87 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { PassThrough } from 'node:stream';
+import { createLocalMcpServer } from '../../server/mcp/server.js';
+import { createApiFetch } from '../../server/mcp/services.js';
+import { parseArgs, serveStdio } from '../../server/mcp/stdio.js';
+
+const usgs = {
+  type: 'FeatureCollection',
+  features: [
+    {
+      id: 'us1',
+      geometry: { type: 'Point', coordinates: [121.5, 24, 10] },
+      properties: { mag: 5.1, place: 'near Hualien', time: 1767229200000 },
+    },
+  ],
+};
+
+test('relative API requests resolve against the configured base', async () => {
+  const seen = [];
+  const apiFetch = createApiFetch({
+    apiBase: 'http://127.0.0.1:5000',
+    fetchImpl: async (url) => seen.push(String(url)),
+  });
+  await apiFetch('/api/launches');
+  await apiFetch('https://earthquake.usgs.gov/feed.geojson');
+  assert.deepEqual(seen, [
+    'http://127.0.0.1:5000/api/launches',
+    'https://earthquake.usgs.gov/feed.geojson',
+  ]);
+  assert.throws(
+    () => createApiFetch({ apiBase: 'file:///etc' }),
+    /http\(s\) URL/,
+  );
+});
+
+test('the stdio server answers newline-delimited requests using only its data sources', async () => {
+  const contacted = [];
+  const server = createLocalMcpServer({
+    apiBase: 'http://127.0.0.1:5000',
+    fetchImpl: async (url) => {
+      contacted.push(new URL(url).origin);
+      return Response.json(usgs);
+    },
+  });
+  const input = new PassThrough();
+  const output = new PassThrough();
+  let written = '';
+  output.on('data', (chunk) => (written += chunk));
+  const served = serveStdio(server, { input, output });
+  input.write(
+    '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18"}}\n',
+  );
+  input.write('{"jsonrpc":"2.0","method":"notifications/initialized"}\n\n');
+  input.write('not json\n');
+  input.write('{"jsonrpc":"2.0","id":2,"method":"tools/list"}\n');
+  input.end(
+    '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"get_earthquakes","arguments":{}}}\n',
+  );
+  await served;
+  const responses = written
+    .trim()
+    .split('\n')
+    .map((line) => JSON.parse(line));
+  const byId = new Map(responses.map((response) => [response.id, response]));
+  assert.equal(responses.length, 4);
+  assert.equal(byId.get(1).result.serverInfo.name, 'gods-eye-view');
+  assert.equal(byId.get(null).error.code, -32700);
+  assert.deepEqual(
+    byId.get(2).result.tools.map((tool) => tool.name),
+    ['get_earthquakes', 'get_active_fires', 'get_recent_launches'],
+  );
+  assert.equal(
+    byId.get(3).result.content[0].text,
+    '1 earthquake of M2.5+ in the last 24 hours worldwide; strongest M5.1 near Hualien.',
+  );
+  // The earthquake feed is fetched directly; nothing else was contacted.
+  assert.deepEqual(contacted, ['https://earthquake.usgs.gov']);
+});
+
+test('command-line arguments are strict', () => {
+  assert.deepEqual(parseArgs([]), {});
+  assert.deepEqual(parseArgs(['--api-base', 'http://localhost:5173']), {
+    apiBase: 'http://localhost:5173',
+  });
+  assert.throws(() => parseArgs(['--port', '1']), /Unknown argument/);
+});