feat: add refinery package and CLI commands

- internal/refinery: Types for Refinery, MergeRequest, queue items
- internal/refinery: Manager with start/stop/status/queue operations
- gt refinery start: Start refinery for a rig (--foreground option)
- gt refinery stop: Stop running refinery
- gt refinery status: Show refinery state and statistics
- gt refinery queue: Show pending merge requests
- Auto-discover polecat work branches as queue items
- JSON output support for status and queue commands

Closes gt-rm3

Generated with Claude Code

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/refinery/types.go

@@ -0,0 +1,117 @@
+// Package refinery provides the merge queue processing agent.
+package refinery
+
+import "time"
+
+// State represents the refinery's running state.
+type State string
+
+const (
+	// StateStopped means the refinery is not running.
+	StateStopped State = "stopped"
+
+	// StateRunning means the refinery is actively processing.
+	StateRunning State = "running"
+
+	// StatePaused means the refinery is paused (not processing new items).
+	StatePaused State = "paused"
+)
+
+// Refinery represents a rig's merge queue processor.
+type Refinery struct {
+	// RigName is the rig this refinery processes.
+	RigName string `json:"rig_name"`
+
+	// State is the current running state.
+	State State `json:"state"`
+
+	// PID is the process ID if running in background.
+	PID int `json:"pid,omitempty"`
+
+	// StartedAt is when the refinery was started.
+	StartedAt *time.Time `json:"started_at,omitempty"`
+
+	// CurrentMR is the merge request currently being processed.
+	CurrentMR *MergeRequest `json:"current_mr,omitempty"`
+
+	// LastMergeAt is when the last successful merge happened.
+	LastMergeAt *time.Time `json:"last_merge_at,omitempty"`
+
+	// Stats contains cumulative statistics.
+	Stats RefineryStats `json:"stats"`
+}
+
+// MergeRequest represents a branch waiting to be merged.
+type MergeRequest struct {
+	// ID is a unique identifier for this merge request.
+	ID string `json:"id"`
+
+	// Branch is the source branch name (e.g., "polecat/Toast/gt-abc").
+	Branch string `json:"branch"`
+
+	// Worker is the polecat that created this branch.
+	Worker string `json:"worker"`
+
+	// IssueID is the beads issue being worked on.
+	IssueID string `json:"issue_id"`
+
+	// SwarmID is the swarm this work belongs to (if any).
+	SwarmID string `json:"swarm_id,omitempty"`
+
+	// TargetBranch is where this should merge (usually integration or main).
+	TargetBranch string `json:"target_branch"`
+
+	// CreatedAt is when the MR was queued.
+	CreatedAt time.Time `json:"created_at"`
+
+	// Status is the current status of the merge request.
+	Status MRStatus `json:"status"`
+
+	// Error contains error details if Status is MRFailed.
+	Error string `json:"error,omitempty"`
+}
+
+// MRStatus represents the status of a merge request.
+type MRStatus string
+
+const (
+	// MRPending means the MR is waiting to be processed.
+	MRPending MRStatus = "pending"
+
+	// MRProcessing means the MR is currently being merged.
+	MRProcessing MRStatus = "processing"
+
+	// MRMerged means the MR was successfully merged.
+	MRMerged MRStatus = "merged"
+
+	// MRFailed means the merge failed (conflict or error).
+	MRFailed MRStatus = "failed"
+
+	// MRSkipped means the MR was skipped (duplicate, outdated, etc).
+	MRSkipped MRStatus = "skipped"
+)
+
+// RefineryStats contains cumulative refinery statistics.
+type RefineryStats struct {
+	// TotalMerged is the total number of successful merges.
+	TotalMerged int `json:"total_merged"`
+
+	// TotalFailed is the total number of failed merges.
+	TotalFailed int `json:"total_failed"`
+
+	// TotalSkipped is the total number of skipped MRs.
+	TotalSkipped int `json:"total_skipped"`
+
+	// TodayMerged is the number of merges today.
+	TodayMerged int `json:"today_merged"`
+
+	// TodayFailed is the number of failures today.
+	TodayFailed int `json:"today_failed"`
+}
+
+// QueueItem represents an item in the merge queue for display.
+type QueueItem struct {
+	Position  int       `json:"position"`
+	MR        *MergeRequest `json:"mr"`
+	Age       string    `json:"age"`
+}