feat(server): integrate MCP queries and investigation messaging

Add project-bound OAuth MCP queries and controlled analysis with scoped evidence,
limits, timeouts and a nearby-model spatial query using EPSG:4326 inputs.
Default nearby searches to 200 meters and five results.

Integrate investigation messaging/presentation, health/readiness and typed history;
remove duplicate web search and fix online simulation and compressed baseline writes.
Include project migrations 023-025; keep local credentials and demo seeding excluded.

Validation: 319 focused pytest checks; real PostGIS temporary-table regression;
read-only Jinqian bridge radius comparison; cross-language MCP discovery/calls.

app/domain/schemas/agent_messages.py

@@ -0,0 +1,59 @@
+"""Private, durable messages between an ordinary chat and one investigation run."""
+from typing import Annotated, Literal
+from uuid import UUID
+
+from pydantic import Field
+
+from app.domain.schemas.shared import NonEmptyStr, StrictModel
+from app.domain.schemas.workbench_runtime import WorkbenchDateTime
+
+
+MessageText = Annotated[str, Field(min_length=1, max_length=12000, pattern=r"\S")]
+MessageStatus = Literal["pending", "enqueued", "delivered", "failed"]
+
+
+class AgentMessageCreate(StrictModel):
+    request_id: UUID
+    task_id: UUID
+    run_id: UUID
+    source_session_id: NonEmptyStr
+    text: MessageText
+
+
+class AgentMessageReply(StrictModel):
+    request_id: UUID
+    source_session_id: NonEmptyStr
+    text: MessageText
+
+
+class AgentMessageDelivery(StrictModel):
+    status: Literal["enqueued", "delivered", "failed"]
+    target_session_id: NonEmptyStr | None = None
+    native_message_id: NonEmptyStr | None = None
+    failure_detail: Annotated[str, Field(max_length=500)] | None = None
+
+
+class AgentMessage(StrictModel):
+    project_id: UUID
+    message_id: UUID
+    request_id: UUID
+    task_id: UUID
+    run_id: UUID
+    source_session_id: NonEmptyStr
+    source_owner_id: UUID
+    conversation_owner_id: UUID
+    target_session_id: NonEmptyStr | None = None
+    direction: Literal["to_task", "to_chat"]
+    in_reply_to: UUID | None = None
+    text: MessageText
+    status: MessageStatus
+    native_message_id: NonEmptyStr
+    failure_detail: str | None = None
+    created_at: WorkbenchDateTime
+    updated_at: WorkbenchDateTime
+    delivered_at: WorkbenchDateTime | None = None
+
+
+class AgentMessagePage(StrictModel):
+    items: list[AgentMessage]
+    next_cursor: str | None = None