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/tools/lsp_goto_definition.ts

@@ -0,0 +1,48 @@
+import { z } from 'zod';
+import { readFile } from 'node:fs/promises';
+import type { ToolDef, ToolContext } from './types.js';
+import { resolveWritePath } from '../write_guard.js';
+import { lspManager } from '../lsp/server-manager.js';
+import { gotoDefinition } from '../lsp/operations.js';
+
+const LspGotoDefinitionInput = z.object({
+  file_path: z.string().describe('Path to the source file'),
+  line: z.number().int().nonnegative().describe('0-based line number'),
+  character: z.number().int().nonnegative().describe('0-based character offset'),
+});
+
+type InputT = z.infer<typeof LspGotoDefinitionInput>;
+
+export const lspGotoDefinitionTool: ToolDef<InputT> = {
+  name: 'lsp_goto_definition',
+  description: 'Find the definition of a symbol at a given position in a file.',
+  inputSchema: LspGotoDefinitionInput,
+  jsonSchema: {
+    type: 'function',
+    function: {
+      name: 'lsp_goto_definition',
+      description: 'Find definition of symbol at position',
+      parameters: {
+        type: 'object',
+        properties: {
+          file_path: { type: 'string' },
+          line: { type: 'number' },
+          character: { type: 'number' },
+        },
+        required: ['file_path', 'line', 'character'],
+      },
+    },
+  },
+
+  async execute(input: InputT, projectRoot: string, _context: ToolContext): Promise<unknown> {
+    const resolved = await resolveWritePath(projectRoot, input.file_path);
+    const content = await readFile(resolved, 'utf8');
+    const client = await lspManager.getClient(resolved);
+    if (!client) return { error: 'Unsupported file type' };
+
+    const loc = await gotoDefinition(client, resolved, content, input.line, input.character);
+    if (!loc) return { result: 'No definition found.' };
+
+    return { result: `Defined at ${loc.uri}:${loc.range.start.line + 1}:${loc.range.start.character + 1}` };
+  },
+};