Accept spike 2: MCP HTTP endpoint for workflow and agent tools

Adds POST /mcp endpoint speaking MCP Streamable HTTP (JSON-RPC 2.0)
with 12 tools for workflow management and agent orchestration.
Supports both JSON and SSE response modes. Includes real-time agent
output streaming over SSE, Content-Type validation, and 15 integration
tests (134 total).

Tools: create_story, validate_stories, list_upcoming, get_story_todos,
record_tests, ensure_acceptance, start_agent, stop_agent, list_agents,
get_agent_config, reload_agent_config, get_agent_output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/http/mod.rs

@@ -6,6 +6,7 @@ pub mod chat;
 pub mod context;
 pub mod health;
 pub mod io;
+pub mod mcp;
 pub mod model;
 pub mod workflow;
 
@@ -19,7 +20,7 @@ use context::AppContext;
 use io::IoApi;
 use model::ModelApi;
 use poem::EndpointExt;
-use poem::{Route, get};
+use poem::{Route, get, post};
 use poem_openapi::OpenApiService;
 use project::ProjectApi;
 use std::sync::Arc;
@@ -38,6 +39,10 @@ pub fn build_routes(ctx: AppContext) -> impl poem::Endpoint {
             "/agents/:story_id/:agent_name/stream",
             get(agents_sse::agent_stream),
         )
+        .at(
+            "/mcp",
+            post(mcp::mcp_post_handler).get(mcp::mcp_get_handler),
+        )
         .at("/health", get(health::health))
         .at("/assets/*path", get(assets::embedded_asset))
         .at("/", get(assets::embedded_index))