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/types.ts

@@ -0,0 +1,52 @@
+export interface ToolInputSchema {
+  type: 'object';
+  properties: Record<string, unknown>;
+  required?: string[];
+}
+
+export interface Tool {
+  name: string;
+  description: string;
+  inputSchema: ToolInputSchema;
+  execute(args: unknown): Promise<ToolResult>;
+}
+
+export interface ToolCall {
+  id: string;
+  name: string;
+  args: unknown;
+}
+
+export interface ToolResult {
+  success: boolean;
+  output: string;
+  error?: string;
+}
+
+// Content block for assistant messages containing tool calls
+export interface ToolUseBlock {
+  type: 'tool_use';
+  id: string;
+  name: string;
+  input: unknown;
+}
+
+// Content block for user messages returning tool results
+export interface ToolResultBlock {
+  type: 'tool_result';
+  tool_use_id: string;
+  content: string;
+  is_error?: boolean;
+}
+
+// Message from assistant requesting tool use
+export interface ToolUseMessage {
+  role: 'assistant';
+  content: ToolUseBlock[];
+}
+
+// Message from user returning tool results
+export interface ToolResultMessage {
+  role: 'user';
+  content: ToolResultBlock[];
+}