feat(resources): Add resources/subscribe and resources/unsubscribe support

[getlarge]

Summary

This PR adds MCP spec-compliant resources/subscribe and resources/unsubscribe methods, plus query parameter URI matching for resources with uriSchema.

Closes #96

Changes

1. Custom Subscription Handlers

Applications can now implement their own subscription storage:

// Application manages its own subscription store
const subscriptions = new Map<string, Set<string>>();

app.mcpSetResourceSubscribeHandler(async (params, context) => {
  const subs = subscriptions.get(params.uri) || new Set();
  subs.add(context.sessionId!);
  subscriptions.set(params.uri, subs);
  return {};
});

app.mcpSetResourceUnsubscribeHandler(async (params, context) => {
  const subs = subscriptions.get(params.uri);
  if (subs) subs.delete(context.sessionId!);
  return {};
});

// Notify on resource change via existing mcpSendToSession
const subs = subscriptions.get(changedUri);
for (const sessionId of subs || []) {
  await app.mcpSendToSession(sessionId, {
    jsonrpc: '2.0',
    method: 'notifications/resources/updated',
    params: { uri: changedUri }
  });
}

2. Query Parameter URI Matching

Resources with uriSchema can now be read with query parameters:

app.mcpAddResource({
  uri: 'aip://findings',
  name: 'Findings',
  uriSchema: Type.Object({ id: Type.String() })
}, async (uri, context) => {
  const url = new URL(uri, 'http://x');
  const id = url.searchParams.get('id');
  // ...
});

// Client can now read: 'aip://findings?id=abc123'
// Falls back to 'aip://findings' base URI because it has uriSchema

Files Changed

• src/types.ts - Add subscription handler types and Fastify declaration
• src/decorators/meta.ts - Add setter decorators
• src/handlers.ts - Add subscription handlers and query param fallback
• src/index.ts - Create and pass resourceHandlers
• src/routes/mcp.ts - Include resourceHandlers in dependencies
• test/integration.test.ts - Fix type guards (cherry-picked)

Design Decisions

1. Custom handlers, not built-in tracking - Applications manage their own storage
2. METHOD_NOT_FOUND when not configured - Clear signal that feature isn't enabled
3. uriSchema as query param indicator - Only falls back if resource expects params

Backwards Compatibility

• Existing mcpAddResource registrations unchanged
• Default resources/read behavior unchanged for exact matches
• New decorators are optional

Test Plan

• TypeScript compiles (npm run typecheck)
• Existing tests pass (npm run test)
• Manual testing with MCP client

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🤖 Generated with Claude Code

[mcollina]

lgtm