feat: implement tweaks plan - modals, smart shell, spinner, /models, debug log, skills

Phase 1: Permission modal dialog, session resume modal, HistoryInput with
up/down arrow cycling, remove "You:" echo from chat log, LLM client cleanup
on unmount.

Phase 2: Smart shell auto-approve using allowed/denied command lists from
ToolsConfig, animated thinking spinner with live token count in status bar.

Phase 3: /models slash command (list + switch), CLI directory positional
argument, JSONL debug logger with rotation.

Phase 4: Skills system with SkillsManager, load_skill LLM tool, /skills
listing, skill invocation via slash commands, system prompt integration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/tools/registry.py

@@ -1,12 +1,17 @@
 """Tool registration and schema export."""
 
+from __future__ import annotations
+
 import logging
 from pathlib import Path
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 from app.models.config import AppConfig
 from app.tools.base import BaseTool
 
+if TYPE_CHECKING:
+    from app.services.skills import SkillsManager
+
 logger = logging.getLogger(__name__)
 
 
@@ -36,7 +41,11 @@ class ToolRegistry:
         return [tool.get_openai_schema() for tool in self._tools.values()]
 
 
-def create_default_registry(workspace_root: Path, config: AppConfig) -> ToolRegistry:
+def create_default_registry(
+    workspace_root: Path,
+    config: AppConfig,
+    skills_manager: SkillsManager | None = None,
+) -> ToolRegistry:
     """Create a ToolRegistry populated with all built-in tools."""
     # Read tools
     from app.tools.filesystem import ListDirTool, ReadFileTool
@@ -81,4 +90,10 @@ def create_default_registry(workspace_root: Path, config: AppConfig) -> ToolRegi
     # Control flow
     registry.register(FinishTool(workspace_root, config))
 
+    # Skills (conditional)
+    if skills_manager is not None:
+        from app.tools.skills import LoadSkillTool
+
+        registry.register(LoadSkillTool(workspace_root, config, skills_manager))
+
     return registry