feat(executor): per-task agent MCP server + token registry (Phase 2)

Adds the agent-facing MCP transport foundation: a Registry that mints a
per-task bearer token bound to a freshly built MCP server exposing the four
agent tools (ask_user, report_summary, spawn_subtask, record_progress), and
an HTTP handler (StreamableHTTP) that resolves the token to that server. The
server never trusts an agent-supplied task ID — context comes from the token.

The default storeChannel now buffers summary and question signals under a
mutex (an MCP tool call lands on an HTTP-handler goroutine mid-run), exposing
ReportedSummary/PendingQuestion. The pool flushes the buffered summary onto
the execution after the run, replacing the runner's direct exec.Summary write
and keeping the read race-free.

ask_user follows the record-and-resume model: it buffers the question, returns
ErrAgentBlocked, and the tool tells the agent to end its turn; the run blocks
and resumes later via claude --resume (no live slot held).

Tests cover registry lifecycle, in-memory tool dispatch, and HTTP end-to-end
with bearer auth (valid token dispatches; invalid token rejected).

Not yet wired into the runners or mounted on the API server — next increment.

https://claude.ai/code/session_01SESwn7kQ7oP62trWw6pc39

1 files changed, 7 insertions, 7 deletions

diff --git a/internal/executor/gemini_test.go b/internal/executor/gemini_test.go
index c8f7422..a906f2c 100644
--- a/internal/executor/gemini_test.go
+++ b/internal/executor/gemini_test.go
@@ -125,7 +125,7 @@ func TestGeminiRunner_Run_InaccessibleProjectDir_ReturnsError(t *testing.T) {
 	}
 	exec := &storage.Execution{ID: "test-exec"}
 
-	err := r.Run(context.Background(), tk, exec, newStoreChannel(nil, tk.ID, exec))
+	err := r.Run(context.Background(), tk, exec, newStoreChannel(nil, tk.ID))
 
 	if err == nil {
 		t.Fatal("expected error for inaccessible project_dir, got nil")
@@ -213,7 +213,7 @@ func TestGeminiRunner_Run_ProjectDir_RunsInSandbox(t *testing.T) {
 	}
 	e := &storage.Execution{ID: "sandbox-exec", TaskID: "task-1"}
 
-	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID, e)); err != nil {
+	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID)); err != nil {
 		t.Fatalf("Run: %v", err)
 	}
 
@@ -261,7 +261,7 @@ fi
 	}
 	e := &storage.Execution{ID: "blocked-gemini-exec", TaskID: "task-1"}
 
-	err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID, e))
+	err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID))
 
 	var blocked *BlockedError
 	if !errors.As(err, &blocked) {
@@ -301,7 +301,7 @@ func TestGeminiRunner_Run_ExecError_PreservesSandbox(t *testing.T) {
 	}
 	e := &storage.Execution{ID: "err-gemini-exec", TaskID: "task-1"}
 
-	err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID, e))
+	err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID))
 	if err == nil {
 		t.Fatal("expected error from failing gemini exit")
 	}
@@ -352,7 +352,7 @@ func TestGeminiRunner_Run_ResumeUsesStoredSandboxDir(t *testing.T) {
 		SandboxDir:      sandboxDir,
 	}
 
-	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID, e)); err != nil {
+	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID)); err != nil {
 		t.Fatalf("Run with preserved sandbox: %v", err)
 	}
 
@@ -400,7 +400,7 @@ func TestGeminiRunner_Run_StaleSandboxDir_ClonesAfresh(t *testing.T) {
 		SandboxDir:      staleSandbox,
 	}
 
-	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID, e)); err != nil {
+	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID)); err != nil {
 		t.Fatalf("Run with stale sandbox: %v", err)
 	}
 
@@ -438,7 +438,7 @@ func TestGeminiRunner_Run_NoProjectDir_SkipsSandbox(t *testing.T) {
 	}
 	e := &storage.Execution{ID: "no-pd-gemini", TaskID: "task-nopd"}
 
-	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID, e)); err != nil {
+	if err := r.Run(context.Background(), tk, e, newStoreChannel(nil, tk.ID)); err != nil {
 		t.Fatalf("Run without project_dir: %v", err)
 	}
 	if e.SandboxDir != "" {