feat(executor,api): wire agent MCP into ContainerRunner + mount /mcp (Phase 2)

ContainerRunner now mints a per-task MCP token (from an injected Registry),
writes a claude mcp-config into the workspace pointing at the host agent MCP
server over host.docker.internal with that bearer, and adds --mcp-config to the
in-container claude invocation. The token is revoked when the run ends. After
the run, a buffered ask_user (PendingQuestion on the channel) is converted into
a BlockedError — the MCP path to BLOCKED — with the file-based question.json
kept as a fallback for in-flight tasks started on the old wire.

The API server mounts the StreamableHTTP MCP handler at POST/GET/DELETE /mcp
when a registry is provided; serve.go constructs one Registry shared by the
runners (mint) and the server (resolve). Minting is skipped for gemini agents.

Tests: writeMCPConfig output shape, buildInnerCmd flag presence/absence, and an
api-level end-to-end MCP tool call through NewServer/Handler proving the route
is mounted (and absent without a registry).

https://claude.ai/code/session_01SESwn7kQ7oP62trWw6pc39

1 files changed, 2 insertions, 2 deletions

diff --git a/internal/api/server_test.go b/internal/api/server_test.go
index f902495..dd6eed5 100644
--- a/internal/api/server_test.go
+++ b/internal/api/server_test.go
@@ -98,7 +98,7 @@ func testServerWithRunner(t *testing.T, runner executor.Runner) (*Server, *stora
 		"gemini": runner,
 	}
 	pool := executor.NewPool(2, runners, store, logger)
-	srv := NewServer(store, pool, logger, "claude", "gemini")
+	srv := NewServer(store, pool, nil, logger, "claude", "gemini")
 	return srv, store
 }
 
@@ -194,7 +194,7 @@ func testServerWithGeminiMockRunner(t *testing.T) (*Server, *storage.DB) {
 		"gemini": mr,
 	}
 	pool := executor.NewPool(2, runners, store, logger)
-	srv := NewServer(store, pool, logger, "claude", "gemini")
+	srv := NewServer(store, pool, nil, logger, "claude", "gemini")
 	return srv, store
 }