feat(mcp): scaffold three project context tools

mcp_servers/project_context/foundation.py

@@ -0,0 +1,106 @@
+"""Shared, stable boundary used by all Project Context tool work packages."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from dataclasses import dataclass
+from datetime import datetime
+from typing import Any, Protocol
+
+from pydantic import AnyUrl, BaseModel, ConfigDict, Field
+
+
+class ContractModel(BaseModel):
+    """Strict immutable model so provider-specific fields cannot leak to the Agent."""
+
+    model_config = ConfigDict(extra="forbid", frozen=True)
+
+
+class IdentityContext(ContractModel):
+    actor_id: str = Field(min_length=1, max_length=256)
+    org_unit: str = Field(min_length=1, max_length=128)
+    customer: str = Field(min_length=1, max_length=128)
+    project: str = Field(min_length=1, max_length=128)
+    granted_scopes: frozenset[str]
+
+
+class SourceCitation(ContractModel):
+    system: str = Field(min_length=1, max_length=64)
+    url: AnyUrl
+    revision: str = Field(min_length=1, max_length=256)
+    retrieved_at: datetime
+
+
+@dataclass(frozen=True)
+class DispatchResult:
+    ok: bool
+    payload: dict[str, Any]
+
+
+class PolicyDecisionPoint(Protocol):
+    def decide(self, identity: IdentityContext, tool_name: str, project_id: str) -> bool: ...
+
+
+class CredentialResolver(Protocol):
+    def resolve(self, identity: IdentityContext, tool_name: str) -> Any: ...
+
+
+@dataclass(frozen=True)
+class ProjectContextRuntime:
+    identity: IdentityContext
+    policy: PolicyDecisionPoint
+    credential_resolver: CredentialResolver
+
+
+class ProviderError(RuntimeError):
+    """A provider failure with a caller-safe message and retry classification."""
+
+    def __init__(self, code: str, message: str, *, retryable: bool) -> None:
+        super().__init__(message)
+        self.code = code
+        self.safe_message = message
+        self.retryable = retryable
+
+
+ToolHandler = Callable[[ContractModel, Any], dict[str, Any]]
+
+
+@dataclass(frozen=True)
+class ToolTemplate:
+    name: str
+    description: str
+    input_model: type[ContractModel]
+    output_model: type[ContractModel]
+    handler: ToolHandler
+
+    def declaration(self) -> dict[str, Any]:
+        return {
+            "name": self.name,
+            "description": self.description,
+            "inputSchema": self.input_model.model_json_schema(),
+            "outputSchema": self.output_model.model_json_schema(),
+        }
+
+
+def error_result(
+    code: str,
+    *,
+    category: str,
+    retryable: bool,
+    message: str,
+    suggested_action: str,
+    correlation_id: str,
+) -> DispatchResult:
+    return DispatchResult(
+        ok=False,
+        payload={
+            "error": {
+                "code": code,
+                "category": category,
+                "retryable": retryable,
+                "message": message,
+                "suggested_action": suggested_action,
+                "correlation_id": correlation_id,
+            }
+        },
+    )