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/utils/tui-app/paste-utils.ts

@@ -79,6 +79,7 @@ export const addPastedBlock = (
     newState: {
       pastedBlocks: newBlocks,
       pasteCounter: newCounter,
+      pastedImages: state.pastedImages ?? [],
     },
     pastedContent,
   };
@@ -201,9 +202,10 @@ export const normalizeLineEndings = (text: string): string => {
 };
 
 /**
- * Clears all pasted blocks
+ * Clears all pasted blocks and images
  */
 export const clearPastedBlocks = (): PasteState => ({
   pastedBlocks: new Map(),
   pasteCounter: 0,
+  pastedImages: [],
 });