feat: add custom HeaderPanel widget and switchable agent modes

Replace built-in Header with a custom HeaderPanel showing model name,
mode badge, and live token usage. Add AgentMode enum (normal/plan/auto)
with mode-aware permission gating — Plan mode restricts to read-only
tools, Auto mode auto-approves everything. Includes /mode slash command
and Ctrl+P keybinding to cycle modes.

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

app/ui/app.py

@@ -10,18 +10,19 @@ from rich.panel import Panel
 from rich.text import Text
 from textual.app import App, ComposeResult
 from textual.binding import Binding
-from textual.widgets import Header, Input, RichLog
+from textual.widgets import Input, RichLog
 from textual import work
 
 from app.agent.context import SessionContext
 from app.agent.loop import AgentLoop
-from app.models.config import AppConfig
+from app.models.config import AgentMode, AppConfig
 from app.services.llm import LLMClient
 from app.services.permissions import PermissionsService
 from app.services.session import SessionManager
 from app.services.streaming import StreamHandler
 from app.tools.registry import create_default_registry
 from app.ui.widgets import (
+    HeaderPanel,
     HistoryInput,
     PermissionModal,
     SessionResumeModal,
@@ -45,6 +46,7 @@ class SneakyCodeApp(App):
 
     BINDINGS = [
         Binding("ctrl+c", "cancel_or_quit", "Cancel/Quit", show=False),
+        Binding("ctrl+p", "cycle_mode", "Cycle Mode"),
     ]
 
     def __init__(self, config: AppConfig, session_mgr: SessionManager | None = None) -> None:
@@ -61,10 +63,9 @@ class SneakyCodeApp(App):
         self._skill_runner = None
         self._current_worker: Worker | None = None
         self._cancel_count = 0
-        self.sub_title = config.llm.model
 
     def compose(self) -> ComposeResult:
-        yield Header()
+        yield HeaderPanel(model_name=self._config.llm.model)
         yield RichLog(id="chat-log", highlight=True, markup=True)
         yield StreamingStatic("", id="streaming")
         yield StatusBar()
@@ -190,6 +191,8 @@ class SneakyCodeApp(App):
             table.add_row("/session", "Show session info (messages, tokens, start time)")
             table.add_row("/models", "List available Ollama models")
             table.add_row("/models <name>", "Switch to a different model")
+            table.add_row("/mode", "Show current agent mode")
+            table.add_row("/mode normal|plan|auto", "Switch agent mode")
             table.add_row("/skills", "List available skills")
             table.add_row("/<skill>", "Load a skill by name")
             log.write(table)
@@ -243,8 +246,23 @@ class SneakyCodeApp(App):
             else:
                 new_model = parts[1].strip()
                 self._config.llm.model = new_model
-                self.sub_title = new_model
+                self.query_one(HeaderPanel).update_model(new_model)
                 log.write(Text(f"Switched to model: {new_model}", style="bold green"))
+        elif cmd.startswith("/mode"):
+            parts = command.split(maxsplit=1)
+            if len(parts) == 1:
+                current = self._permissions.mode
+                log.write(Text(f"Current mode: {current.value}", style="cyan"))
+            else:
+                mode_str = parts[1].strip().lower()
+                try:
+                    new_mode = AgentMode(mode_str)
+                except ValueError:
+                    log.write(Text(f"Unknown mode: {mode_str}. Use normal, plan, or auto.", style="yellow"))
+                    return
+                self._permissions.mode = new_mode
+                self.query_one(HeaderPanel).update_mode(new_mode)
+                log.write(Text(f"Switched to {new_mode.value} mode", style="bold green"))
         elif cmd == "/skills":
             if self._skills_manager:
                 skills = self._skills_manager.list_skills()
@@ -306,12 +324,19 @@ class SneakyCodeApp(App):
         status_bar.start_streaming()
 
         # Set up streaming UI callbacks
+        header = self.query_one(HeaderPanel)
+
         def on_content(content: str) -> None:
             streaming_widget.update(
                 Panel(Markdown(content), title="Assistant", border_style="green", expand=True)
             )
             streaming_widget.show_streaming()
-            status_bar.update_stream_tokens(len(content) // 4)
+            stream_tokens = len(content) // 4
+            status_bar.update_stream_tokens(stream_tokens)
+            header.update_tokens(
+                self._ctx.estimated_tokens + stream_tokens,
+                self._ctx.token_counter.budget,
+            )
 
         def on_thinking() -> None:
             streaming_widget.update(Text("Thinking...", style="dim"))
@@ -335,6 +360,10 @@ class SneakyCodeApp(App):
 
         status_bar.stop_streaming()
 
+        # Update token display in header
+        header = self.query_one(HeaderPanel)
+        header.update_tokens(self._ctx.estimated_tokens, self._ctx.token_counter.budget)
+
         # Update skill indicator (skill may have been deactivated via finish_skill)
         if self._skill_runner and not self._skill_runner.is_active:
             status_bar.set_active_skill(None)
@@ -360,6 +389,21 @@ class SneakyCodeApp(App):
             log = self.query_one("#chat-log", RichLog)
             log.write(Text("⚠ Cancelling... (press Ctrl+C again to quit)", style="yellow"))
 
+    def action_cycle_mode(self) -> None:
+        """Cycle through agent modes: Normal → Plan → Auto → Normal."""
+        if self._permissions is None:
+            return
+        cycle = {
+            AgentMode.NORMAL: AgentMode.PLAN,
+            AgentMode.PLAN: AgentMode.AUTO,
+            AgentMode.AUTO: AgentMode.NORMAL,
+        }
+        new_mode = cycle[self._permissions.mode]
+        self._permissions.mode = new_mode
+        self.query_one(HeaderPanel).update_mode(new_mode)
+        log = self.query_one("#chat-log", RichLog)
+        log.write(Text(f"Mode: {new_mode.value}", style="bold green"))
+
     async def on_unmount(self) -> None:
         """Clean up the LLM client on app shutdown."""
         if self._client is not None: