feat(coder): add LSP code intelligence tools

- lsp/ module: types, config, JSON-RPC client, server-manager, operations
- lsp_diagnostics: TypeScript/JavaScript diagnostics for a file
- lsp_goto_definition: find symbol definition at position
- lsp_find_references: find all references to a symbol
- Registered as READ_TOOLS in tool index

apps/coder/src/services/lsp/client.ts

@@ -0,0 +1,75 @@
+import { createInterface } from 'node:readline';
+import type { Readable, Writable } from 'node:stream';
+
+interface RpcRequest {
+  jsonrpc: '2.0';
+  id: number;
+  method: string;
+  params?: unknown;
+}
+
+interface RpcResponse {
+  jsonrpc: '2.0';
+  id: number;
+  result?: unknown;
+  error?: { code: number; message: string };
+}
+
+export class LspClient {
+  private nextId = 1;
+  private pending = new Map<number, { resolve: (v: RpcResponse) => void; reject: (e: Error) => void }>();
+  private buffer = '';
+
+  constructor(
+    private stdin: Writable,
+    private stdout: Readable,
+  ) {
+    const rl = createInterface({ input: stdout, crlfDelay: Infinity });
+    rl.on('line', (line) => this.handleLine(line));
+  }
+
+  private handleLine(line: string): void {
+    this.buffer += line + '\n';
+    const match = this.buffer.match(/Content-Length: (\d+)\r?\n\r?\n/);
+    if (!match || !match[1]) return;
+    const len = parseInt(match[1], 10);
+    const headerEnd = match.index! + match[0].length;
+    const body = this.buffer.slice(headerEnd, headerEnd + len);
+    if (body.length < len) return;
+    this.buffer = this.buffer.slice(headerEnd + len);
+    try {
+      const msg: RpcResponse = JSON.parse(body);
+      const cb = this.pending.get(msg.id);
+      if (cb) {
+        this.pending.delete(msg.id);
+        cb.resolve(msg);
+      }
+    } catch {
+      // Malformed JSON, ignore
+    }
+  }
+
+  async request(method: string, params?: unknown): Promise<unknown> {
+    const id = this.nextId++;
+    const req: RpcRequest = { jsonrpc: '2.0', id, method, params };
+    const body = JSON.stringify(req);
+    const header = `Content-Length: ${Buffer.byteLength(body, 'utf8')}\r\n\r\n`;
+
+    return new Promise((resolve, reject) => {
+      this.pending.set(id, {
+        resolve: (resp) => {
+          if (resp.error) reject(new Error(resp.error.message));
+          else resolve(resp.result);
+        },
+        reject,
+      });
+      this.stdin.write(header + body);
+    });
+  }
+
+  async notify(method: string, params?: unknown): Promise<void> {
+    const body = JSON.stringify({ jsonrpc: '2.0', method, params });
+    const header = `Content-Length: ${Buffer.byteLength(body, 'utf8')}\r\n\r\n`;
+    this.stdin.write(header + body);
+  }
+}