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/subagent.py

@@ -12,15 +12,13 @@ from loguru import logger
 
 from nanobot.agent.hook import AgentHook, AgentHookContext
 from nanobot.agent.runner import AgentRunner, AgentRunSpec
-from nanobot.agent.skills import BUILTIN_SKILLS_DIR
-from nanobot.agent.tools.filesystem import EditFileTool, ListDirTool, ReadFileTool, WriteFileTool
+from nanobot.agent.tools.context import ToolContext
+from nanobot.agent.tools.file_state import FileStates
+from nanobot.agent.tools.loader import ToolLoader
 from nanobot.agent.tools.registry import ToolRegistry
-from nanobot.agent.tools.search import GlobTool, GrepTool
-from nanobot.agent.tools.shell import ExecTool
-from nanobot.agent.tools.web import WebFetchTool, WebSearchTool
 from nanobot.bus.events import InboundMessage
 from nanobot.bus.queue import MessageBus
-from nanobot.config.schema import AgentDefaults, ExecToolConfig, WebToolsConfig
+from nanobot.config.schema import AgentDefaults, ToolsConfig
 from nanobot.providers.base import LLMProvider
 from nanobot.utils.prompt_templates import render_template
 
@@ -77,8 +75,7 @@ class SubagentManager:
         bus: MessageBus,
         max_tool_result_chars: int,
         model: str | None = None,
-        web_config: "WebToolsConfig | None" = None,
-        exec_config: "ExecToolConfig | None" = None,
+        tools_config: ToolsConfig | None = None,
         restrict_to_workspace: bool = False,
         disabled_skills: list[str] | None = None,
         max_iterations: int | None = None,
@@ -88,9 +85,8 @@ class SubagentManager:
         self.workspace = workspace
         self.bus = bus
         self.model = model or provider.get_default_model()
-        self.web_config = web_config or WebToolsConfig()
+        self.tools_config = tools_config or ToolsConfig()
         self.max_tool_result_chars = max_tool_result_chars
-        self.exec_config = exec_config or ExecToolConfig()
         self.restrict_to_workspace = restrict_to_workspace
         self.disabled_skills = set(disabled_skills or [])
         self.max_iterations = (
@@ -103,6 +99,29 @@ class SubagentManager:
         self._running_tasks: dict[str, asyncio.Task[None]] = {}
         self._task_statuses: dict[str, SubagentStatus] = {}
         self._session_tasks: dict[str, set[str]] = {}  # session_key -> {task_id, ...}
+        self._tools_cache: ToolRegistry | None = None
+
+    def _subagent_tools_config(self) -> ToolsConfig:
+        """Build a ToolsConfig scoped for subagent use."""
+        return ToolsConfig(
+            exec=self.tools_config.exec,
+            web=self.tools_config.web,
+            restrict_to_workspace=self.restrict_to_workspace,
+        )
+
+    def _build_tools(self) -> ToolRegistry:
+        """Build the subagent tool registry via ToolLoader (cached)."""
+        if self._tools_cache is not None:
+            return self._tools_cache
+        registry = ToolRegistry()
+        ctx = ToolContext(
+            config=self._subagent_tools_config(),
+            workspace=str(self.workspace),
+            file_state_store=FileStates(),
+        )
+        ToolLoader().load(ctx, registry, scope="subagent")
+        self._tools_cache = registry
+        return registry
 
     def set_provider(self, provider: LLMProvider, model: str) -> None:
         self.provider = provider
@@ -168,46 +187,7 @@ class SubagentManager:
             status.iteration = payload.get("iteration", status.iteration)
 
         try:
-            # Build subagent tools (no message tool, no spawn tool)
-            tools = ToolRegistry()
-            allowed_dir = self.workspace if (self.restrict_to_workspace or self.exec_config.sandbox) else None
-            extra_read = [BUILTIN_SKILLS_DIR] if allowed_dir else None
-            # Subagent gets its own FileStates so its read-dedup cache is
-            # isolated from the parent loop's sessions (issue #3571).
-            from nanobot.agent.tools.file_state import FileStates
-            file_states = FileStates()
-            tools.register(ReadFileTool(workspace=self.workspace, allowed_dir=allowed_dir, extra_allowed_dirs=extra_read, file_states=file_states))
-            tools.register(WriteFileTool(workspace=self.workspace, allowed_dir=allowed_dir, file_states=file_states))
-            tools.register(EditFileTool(workspace=self.workspace, allowed_dir=allowed_dir, file_states=file_states))
-            tools.register(ListDirTool(workspace=self.workspace, allowed_dir=allowed_dir, file_states=file_states))
-            tools.register(GlobTool(workspace=self.workspace, allowed_dir=allowed_dir, file_states=file_states))
-            tools.register(GrepTool(workspace=self.workspace, allowed_dir=allowed_dir, file_states=file_states))
-            if self.exec_config.enable:
-                tools.register(ExecTool(
-                    working_dir=str(self.workspace),
-                    timeout=self.exec_config.timeout,
-                    restrict_to_workspace=self.restrict_to_workspace,
-                    sandbox=self.exec_config.sandbox,
-                    path_append=self.exec_config.path_append,
-                    allowed_env_keys=self.exec_config.allowed_env_keys,
-                    allow_patterns=self.exec_config.allow_patterns,
-                    deny_patterns=self.exec_config.deny_patterns,
-                ))
-            if self.web_config.enable:
-                tools.register(
-                    WebSearchTool(
-                        config=self.web_config.search,
-                        proxy=self.web_config.proxy,
-                        user_agent=self.web_config.user_agent,
-                    )
-                )
-                tools.register(
-                    WebFetchTool(
-                        config=self.web_config.fetch,
-                        proxy=self.web_config.proxy,
-                        user_agent=self.web_config.user_agent,
-                    )
-                )
+            tools = self._build_tools()
             system_prompt = self._build_subagent_prompt()
             messages: list[dict[str, Any]] = [
                 {"role": "system", "content": system_prompt},