feat(executor): introduce AgentChannel seam for runner signals

Defines AgentChannel — the normalized interface by which a runner reports
agent-originated signals (AskUser, ReportSummary, SpawnSubtask,
RecordProgress) — plus a default storeChannel implementation backed by
storage. Runner.Run now takes an AgentChannel; the pool constructs one
per execution.

The file transport routes its post-exit summary detection through
ch.ReportSummary (buffered onto the execution so the pool still applies
its extract/synthesize fallbacks, no double-write). AskUser returns
ErrAgentBlocked since write-and-exit cannot answer in-session; question
persistence stays with the pool's BlockedError handling. SpawnSubtask
and RecordProgress are implemented and tested, ready for the MCP
transport in Phase 2 where the channel becomes fully load-bearing.

Store gains CreateEvent so the channel can emit agent_message events.

https://claude.ai/code/session_01SESwn7kQ7oP62trWw6pc39

1 files changed, 8 insertions, 4 deletions

diff --git a/internal/executor/executor.go b/internal/executor/executor.go
index 09169bd..76e67b8 100644
--- a/internal/executor/executor.go
+++ b/internal/executor/executor.go
@@ -12,6 +12,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/thepeterstone/claudomator/internal/event"
 	"github.com/thepeterstone/claudomator/internal/llm"
 	"github.com/thepeterstone/claudomator/internal/retry"
 	"github.com/thepeterstone/claudomator/internal/storage"
@@ -41,6 +42,7 @@ type Store interface {
 	ListTasksByStory(storyID string) ([]*task.Task, error)
 	UpdateStoryStatus(id string, status task.StoryState) error
 	CreateTask(t *task.Task) error
+	CreateEvent(e *event.Event) error
 	UpdateTaskCheckerReport(id, report string) error
 	GetCheckerTask(checkedTaskID string) (*task.Task, error)
 }
@@ -52,9 +54,11 @@ type LogPather interface {
 	ExecLogDir(execID string) string
 }
 
-// Runner executes a single task and returns the result.
+// Runner executes a single task and returns the result. The AgentChannel is how
+// the runner reports agent-originated signals (summary, questions, subtasks,
+// progress) back to the system.
 type Runner interface {
-	Run(ctx context.Context, t *task.Task, exec *storage.Execution) error
+	Run(ctx context.Context, t *task.Task, exec *storage.Execution, ch AgentChannel) error
 }
 
 // workItem is an entry in the pool's internal work queue.
@@ -352,7 +356,7 @@ func (p *Pool) executeResume(ctx context.Context, t *task.Task, exec *storage.Ex
 		}
 	}
 
-	err = runner.Run(ctx, t, exec)
+	err = runner.Run(ctx, t, exec, newStoreChannel(p.store, t.ID, exec))
 	exec.EndTime = time.Now().UTC()
 
 	p.decActiveAgent(agentType, &cleaned)
@@ -1073,7 +1077,7 @@ func (p *Pool) execute(ctx context.Context, t *task.Task) {
 	}
 
 	// Run the task.
-	err = runner.Run(ctx, t, exec)
+	err = runner.Run(ctx, t, exec, newStoreChannel(p.store, t.ID, exec))
 	exec.EndTime = time.Now().UTC()
 
 	p.decActiveAgent(agentType, &cleaned)