feat: implement hooks, plugins, session forks, and vim motions

Add 4 major features to codetyper-cli:

- Hooks System: Lifecycle hooks (PreToolUse, PostToolUse, SessionStart,
  SessionEnd, UserPromptSubmit, Stop) with exit code control flow
- Plugin System: Custom tools, commands, and hooks via plugin manifest
- Session Forking: Snapshots, rewind, fork, and switch between branches
- Vim Motions: Normal/Insert/Command/Visual modes with keyboard navigation

New files:
- src/types/{hooks,plugin,session-fork,vim}.ts
- src/constants/{hooks,plugin,session-fork,vim}.ts
- src/services/{hooks-service,plugin-loader,plugin-service,session-fork-service}.ts
- src/stores/vim-store.ts (vanilla)
- src/tui/hooks/{useVimMode,useVimStore,useTodoStore,useThemeStore}.ts
- src/tui/components/VimStatusLine.tsx

Modified:
- src/services/agent.ts (hook integration)
- src/tools/index.ts (plugin tool registration)
- src/stores/{todo-store,theme-store}.ts (converted to vanilla)
- TUI components (updated hook imports)

src/types/hooks.ts

@@ -0,0 +1,159 @@
+/**
+ * Hook System Type Definitions
+ *
+ * Types for lifecycle hooks that can intercept tool execution
+ */
+
+/**
+ * Available hook event types
+ */
+export type HookEventType =
+  | "PreToolUse"
+  | "PostToolUse"
+  | "SessionStart"
+  | "SessionEnd"
+  | "UserPromptSubmit"
+  | "Stop";
+
+/**
+ * Hook definition from configuration
+ */
+export interface HookDefinition {
+  /** Event type to trigger on */
+  event: HookEventType;
+  /** Path to bash script (relative to project root or absolute) */
+  script: string;
+  /** Timeout in milliseconds (default 30000) */
+  timeout?: number;
+  /** Whether the hook is enabled (default true) */
+  enabled?: boolean;
+  /** Optional name for logging/debugging */
+  name?: string;
+}
+
+/**
+ * Configuration for hooks
+ */
+export interface HooksConfig {
+  hooks: HookDefinition[];
+}
+
+/**
+ * Result of hook execution
+ */
+export type HookResult =
+  | HookResultAllow
+  | HookResultWarn
+  | HookResultBlock
+  | HookResultModify;
+
+export interface HookResultAllow {
+  action: "allow";
+}
+
+export interface HookResultWarn {
+  action: "warn";
+  message: string;
+}
+
+export interface HookResultBlock {
+  action: "block";
+  message: string;
+}
+
+export interface HookResultModify {
+  action: "modify";
+  updatedInput: Record<string, unknown>;
+}
+
+/**
+ * Input passed to PreToolUse hooks via stdin
+ */
+export interface PreToolUseHookInput {
+  sessionId: string;
+  toolName: string;
+  toolArgs: Record<string, unknown>;
+  workingDir: string;
+}
+
+/**
+ * Input passed to PostToolUse hooks via stdin
+ */
+export interface PostToolUseHookInput {
+  sessionId: string;
+  toolName: string;
+  toolArgs: Record<string, unknown>;
+  result: {
+    success: boolean;
+    output: string;
+    error?: string;
+  };
+  workingDir: string;
+}
+
+/**
+ * Input passed to SessionStart hooks via stdin
+ */
+export interface SessionStartHookInput {
+  sessionId: string;
+  workingDir: string;
+  provider: string;
+  model: string;
+}
+
+/**
+ * Input passed to SessionEnd hooks via stdin
+ */
+export interface SessionEndHookInput {
+  sessionId: string;
+  workingDir: string;
+  duration: number;
+  messageCount: number;
+}
+
+/**
+ * Input passed to UserPromptSubmit hooks via stdin
+ */
+export interface UserPromptSubmitHookInput {
+  sessionId: string;
+  prompt: string;
+  workingDir: string;
+}
+
+/**
+ * Input passed to Stop hooks via stdin
+ */
+export interface StopHookInput {
+  sessionId: string;
+  workingDir: string;
+  reason: "interrupt" | "complete" | "error";
+}
+
+/**
+ * Union of all hook input types
+ */
+export type HookInput =
+  | PreToolUseHookInput
+  | PostToolUseHookInput
+  | SessionStartHookInput
+  | SessionEndHookInput
+  | UserPromptSubmitHookInput
+  | StopHookInput;
+
+/**
+ * Hook execution context
+ */
+export interface HookExecutionContext {
+  sessionId: string;
+  workingDir: string;
+  event: HookEventType;
+}
+
+/**
+ * Hook execution error
+ */
+export interface HookExecutionError {
+  hook: HookDefinition;
+  error: string;
+  exitCode?: number;
+}