feat: add Pydantic models and EventEmitter for v2 core

- models.py: ProviderConfig, RoleConfig, DiscussionConfig, ScenarioConfig,
  Message, ToolCallRecord, Session — compatible with config.yaml format
- events.py: Event constants, Event dataclass, EventEmitter with on/off/emit
- 67 tests passing (37 models + 30 events)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

meeting_room/events.py

@@ -0,0 +1,129 @@
+"""EventEmitter and event types for the Meeting Room discussion engine.
+
+Synchronous event bus. In Phase 2, an AsyncEventBridge will forward
+events to WebSocket clients.
+"""
+
+from __future__ import annotations
+
+import logging
+from dataclasses import dataclass, field
+from datetime import datetime
+from typing import Any, Callable
+
+logger = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# Event type constants
+# ---------------------------------------------------------------------------
+
+DISCUSSION_START = "discussion_start"
+ROUND_START = "round_start"
+AGENT_TURN_START = "agent_turn_start"
+AGENT_MESSAGE = "agent_message"
+TOOL_CALL = "tool_call"
+TOOL_RESULT = "tool_result"
+AGENT_ERROR = "agent_error"
+ROUND_END = "round_end"
+DISCUSSION_END = "discussion_end"
+BOSS_TURN = "boss_turn"
+
+# ---------------------------------------------------------------------------
+# Event dataclass
+# ---------------------------------------------------------------------------
+
+
+@dataclass
+class Event:
+    """A single event emitted by the discussion engine."""
+
+    type: str
+    data: dict[str, Any] = field(default_factory=dict)
+    timestamp: datetime = field(default_factory=datetime.now)
+
+
+# ---------------------------------------------------------------------------
+# EventEmitter
+# ---------------------------------------------------------------------------
+
+# Type alias for handler callbacks
+Handler = Callable[[Event], None]
+
+
+class EventEmitter:
+    """Synchronous pub/sub event bus.
+
+    Usage::
+
+        bus = EventEmitter()
+
+        def on_message(event: Event):
+            print(event.data)
+
+        bus.on(AGENT_MESSAGE, on_message)
+        bus.emit(AGENT_MESSAGE, text="Hello", agent="Alice")
+        bus.off(AGENT_MESSAGE, on_message)
+    """
+
+    def __init__(self) -> None:
+        self._handlers: dict[str, list[Handler]] = {}
+
+    # -- subscription --------------------------------------------------------
+
+    def on(self, event_type: str, handler: Handler) -> Handler:
+        """Subscribe *handler* to *event_type*.
+
+        Returns the handler so callers can use ``off`` with the same
+        reference, or chain calls.
+        """
+        self._handlers.setdefault(event_type, []).append(handler)
+        return handler
+
+    def off(self, event_type: str, handler: Handler) -> None:
+        """Unsubscribe *handler* from *event_type*.
+
+        Silently ignores unknown event types or missing handlers.
+        """
+        handlers = self._handlers.get(event_type)
+        if handlers is None:
+            return
+        try:
+            handlers.remove(handler)
+        except ValueError:
+            pass
+        # Clean up empty lists to avoid unbounded growth
+        if not handlers:
+            del self._handlers[event_type]
+
+    # -- emission ------------------------------------------------------------
+
+    def emit(self, event_type: str, **data: Any) -> Event:
+        """Create an Event and call every subscribed handler synchronously.
+
+        Handlers that raise exceptions are caught and logged; the emitter
+        never crashes due to a bad handler.
+
+        Returns the Event that was emitted (useful for testing).
+        """
+        event = Event(type=event_type, data=data)
+        handlers = self._handlers.get(event_type, [])
+        for handler in handlers:
+            try:
+                handler(event)
+            except Exception:
+                logger.exception(
+                    "Handler %r raised for event %s",
+                    handler,
+                    event_type,
+                )
+        return event
+
+    # -- introspection -------------------------------------------------------
+
+    def handlers(self, event_type: str) -> list[Handler]:
+        """Return a *copy* of the handler list for *event_type*."""
+        return list(self._handlers.get(event_type, []))
+
+    def clear(self) -> None:
+        """Remove all subscriptions."""
+        self._handlers.clear()

meeting_room/models.py

@@ -0,0 +1,124 @@
+"""Pydantic v2 data models for Meeting Room."""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Union
+
+from pydantic import BaseModel, ConfigDict, Field, field_validator
+
+
+# ---------------------------------------------------------------------------
+# Configuration models — must be compatible with config.yaml parsed by
+# yaml.safe_load() so that DiscussionConfig(**yaml_config) works unchanged.
+# ---------------------------------------------------------------------------
+
+
+class ProviderConfig(BaseModel):
+    """A single API provider (OpenAI-compatible endpoint)."""
+
+    model_config = ConfigDict(extra="forbid")
+
+    base_url: str
+    api_key: str
+
+
+class RoleConfig(BaseModel):
+    """A discussion participant role bound to a provider/model."""
+
+    model_config = ConfigDict(extra="forbid")
+
+    name: str
+    provider: str
+    model: str
+    temperature: float = 0.7
+    tools: Union[str, list[str]] = "none"
+    system_prompt: str = ""
+
+    @field_validator("tools", mode="before")
+    @classmethod
+    def _coerce_tools(cls, v: object) -> Union[str, list[str]]:
+        if isinstance(v, str):
+            return v
+        if isinstance(v, list):
+            return [str(item) for item in v]
+        raise ValueError(f"tools must be a string or list of strings, got {type(v).__name__}")
+
+
+class DefaultsConfig(BaseModel):
+    """Default settings inherited by scenarios."""
+
+    model_config = ConfigDict(extra="ignore")
+
+    max_rounds: int = 8
+    language: str = "ru"
+    framework: str = "custom"
+    workdir: str = "."
+
+
+class DiscussionConfig(BaseModel):
+    """Top-level config — the direct counterpart of config.yaml."""
+
+    model_config = ConfigDict(extra="ignore")
+
+    providers: dict[str, ProviderConfig] = Field(default_factory=dict)
+    roles: dict[str, RoleConfig] = Field(default_factory=dict)
+    defaults: DefaultsConfig = Field(default_factory=DefaultsConfig)
+
+
+# ---------------------------------------------------------------------------
+# Scenario model
+# ---------------------------------------------------------------------------
+
+
+class ScenarioConfig(BaseModel):
+    """A discussion scenario (loaded from .md / .yaml files)."""
+
+    model_config = ConfigDict(extra="ignore")
+
+    name: str = "Untitled"
+    participants: list[str] = Field(default_factory=list)
+    max_rounds: int = 8
+    problem: str = ""
+
+
+# ---------------------------------------------------------------------------
+# Runtime models
+# ---------------------------------------------------------------------------
+
+
+class Message(BaseModel):
+    """A single message in a discussion session."""
+
+    model_config = ConfigDict(extra="forbid")
+
+    role_id: str
+    name: str
+    content: str
+
+
+class ToolCallRecord(BaseModel):
+    """Record of a single tool call made by an agent."""
+
+    model_config = ConfigDict(extra="forbid")
+
+    id: str
+    name: str
+    arguments: str
+    result: str = ""
+
+
+class Session(BaseModel):
+    """A complete discussion session (scenario + messages + timestamps)."""
+
+    model_config = ConfigDict(extra="ignore")
+
+    scenario: ScenarioConfig = Field(default_factory=ScenarioConfig)
+    messages: list[Message] = Field(default_factory=list)
+    tool_calls: list[ToolCallRecord] = Field(default_factory=list)
+    created_at: datetime = Field(
+        default_factory=lambda: datetime.now(timezone.utc),
+    )
+    updated_at: datetime = Field(
+        default_factory=lambda: datetime.now(timezone.utc),
+    )