feat(tools): introduce plugin-based tool discovery and runtime context protocol

This commit implements a progressive refactoring of the tool system to support
plugin discovery, scoped loading, and protocol-driven runtime context injection.

Key changes:
- Add Tool ABC metadata (tool_name, _scopes) and ToolContext dataclass for
dependency injection.
- Introduce ToolLoader with pkgutil-based builtin discovery and
entry_points-based third-party plugin loading.
- Add scope filtering (core/subagent/memory) so different contexts load
appropriate tool sets.
- Introduce ContextAware protocol and RequestContext dataclass to replace
hardcoded per-tool context injection in AgentLoop.
- Add RuntimeState / MutableRuntimeState protocols to decouple MyTool from
AgentLoop.
- Migrate all built-in tools to declare scopes and implement create()/enabled()
hooks.
- Migrate MessageTool, SpawnTool, CronTool, and MyTool to ContextAware.
- Refactor AgentLoop to use ToolLoader and protocol-driven context injection.
- Refactor SubagentManager to use ToolLoader(scope="subagent") with per-run
FileStates isolation.
- Register all built-in tools via pyproject.toml entry_points.
- Add comprehensive tests for loader scopes, entry_points, ContextAware,
subagent tools, and runtime state sync.

nanobot/agent/tools/shell.py

@@ -1,5 +1,7 @@
 """Shell execution tool."""
 
+from __future__ import annotations
+
 import asyncio
 import os
 import re
@@ -10,11 +12,13 @@ from pathlib import Path
 from typing import Any
 
 from loguru import logger
+from pydantic import Field
 
 from nanobot.agent.tools.base import Tool, tool_parameters
 from nanobot.agent.tools.sandbox import wrap_command
 from nanobot.agent.tools.schema import IntegerSchema, StringSchema, tool_parameters_schema
 from nanobot.config.paths import get_media_dir
+from nanobot.config.schema import Base
 
 _IS_WINDOWS = sys.platform == "win32"
 
@@ -29,6 +33,17 @@ _WORKSPACE_BOUNDARY_NOTE = (
 )
 
 
+class ExecToolConfig(Base):
+    """Shell exec tool configuration."""
+    enable: bool = True
+    timeout: int = 60
+    path_append: str = ""
+    sandbox: str = ""
+    allowed_env_keys: list[str] = Field(default_factory=list)
+    allow_patterns: list[str] = Field(default_factory=list)
+    deny_patterns: list[str] = Field(default_factory=list)
+
+
 @tool_parameters(
     tool_parameters_schema(
         command=StringSchema("The shell command to execute"),
@@ -47,6 +62,31 @@ _WORKSPACE_BOUNDARY_NOTE = (
 )
 class ExecTool(Tool):
     """Tool to execute shell commands."""
+    _scopes = {"core", "subagent"}
+
+    config_key = "exec"
+
+    @classmethod
+    def config_cls(cls):
+        return ExecToolConfig
+
+    @classmethod
+    def enabled(cls, ctx: Any) -> bool:
+        return ctx.config.exec.enable
+
+    @classmethod
+    def create(cls, ctx: Any) -> Tool:
+        cfg = ctx.config.exec
+        return cls(
+            working_dir=ctx.workspace,
+            timeout=cfg.timeout,
+            restrict_to_workspace=ctx.config.restrict_to_workspace,
+            sandbox=cfg.sandbox,
+            path_append=cfg.path_append,
+            allowed_env_keys=cfg.allowed_env_keys,
+            allow_patterns=cfg.allow_patterns,
+            deny_patterns=cfg.deny_patterns,
+        )
 
     def __init__(
         self,
@@ -276,6 +316,7 @@ class ExecTool(Tool):
                 "TMP": os.environ.get("TMP", f"{sr}\\Temp"),
                 "PATHEXT": os.environ.get("PATHEXT", ".COM;.EXE;.BAT;.CMD"),
                 "PATH": os.environ.get("PATH", f"{sr}\\system32;{sr}"),
+                "PYTHONUNBUFFERED": "1",
                 "APPDATA": os.environ.get("APPDATA", ""),
                 "LOCALAPPDATA": os.environ.get("LOCALAPPDATA", ""),
                 "ProgramData": os.environ.get("ProgramData", ""),
@@ -293,6 +334,7 @@ class ExecTool(Tool):
             "HOME": home,
             "LANG": os.environ.get("LANG", "C.UTF-8"),
             "TERM": os.environ.get("TERM", "dumb"),
+            "PYTHONUNBUFFERED": "1",
         }
         for key in self.allowed_env_keys:
             val = os.environ.get(key)