feat: add tool framework foundation (types, registry, executor, shell tool, model types, SOUL.md)

- Task 0: SOUL.md + loadSystemPrompt() in daemon
- Task 1: Tool type definitions (Tool, ToolCall, ToolResult, etc.)
- Task 2: ToolRegistry with Anthropic/OpenAI serialization
- Task 3: ToolExecutor with hooks, timeout, truncation
- Task 4: shell.exec builtin tool
- Task 8: Model types updated for tool use (ToolDefinition, ModelToolCall, etc.)
- Task 15: Model index exports for tool types

src/tools/builtin/shell.ts

@@ -0,0 +1,48 @@
+import { execFile } from 'child_process';
+import type { Tool, ToolResult } from '../types.js';
+
+interface ShellExecArgs {
+  command: string;
+  cwd?: string;
+  timeout?: number;
+}
+
+export const shellExecTool: Tool = {
+  name: 'shell.exec',
+  description: 'Execute a shell command and return stdout/stderr. Use for running build commands, git operations, system tasks, etc.',
+  inputSchema: {
+    type: 'object',
+    properties: {
+      command: { type: 'string', description: 'The shell command to execute' },
+      cwd: { type: 'string', description: 'Working directory (optional)' },
+      timeout: { type: 'number', description: 'Timeout in milliseconds (default 30000)' },
+    },
+    required: ['command'],
+  },
+  execute: async (rawArgs: unknown): Promise<ToolResult> => {
+    const args = rawArgs as ShellExecArgs;
+    const timeout = args.timeout ?? 30_000;
+
+    return new Promise((resolve) => {
+      execFile('bash', ['-c', args.command], {
+        cwd: args.cwd,
+        timeout,
+        maxBuffer: 1024 * 1024,
+      }, (error, stdout, stderr) => {
+        if (error) {
+          if (error.killed || error.signal === 'SIGTERM') {
+            resolve({ success: false, output: stdout, error: `Command timed out after ${timeout}ms` });
+            return;
+          }
+          resolve({
+            success: false,
+            output: stdout,
+            error: stderr || error.message,
+          });
+          return;
+        }
+        resolve({ success: true, output: stdout + (stderr ? `\nstderr: ${stderr}` : '') });
+      });
+    });
+  },
+};