refactor: split mq.go (1738 lines) into focused modules

- mq.go (400): commands, flags, init, shared helpers
- mq_integration.go (606): integration branch create/land/status
- mq_status.go (357): status display and formatting
- mq_submit.go (219): submit command and branch parsing
- mq_list.go (206): list command and filtering

Also adds unit tests for helper functions:
- formatStatus, getStatusIcon, formatTimeAgo
- filterMRsByTarget with edge cases
- Test utilities for mocking beads

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/cmd/mq_testutil_test.go

@@ -0,0 +1,96 @@
+package cmd
+
+import (
+	"github.com/steveyegge/gastown/internal/beads"
+)
+
+// mockBeads is a test double for beads.Beads
+type mockBeads struct {
+	issues    map[string]*beads.Issue
+	listFunc  func(opts beads.ListOptions) ([]*beads.Issue, error)
+	showFunc  func(id string) (*beads.Issue, error)
+	closeFunc func(id string) error
+}
+
+func newMockBeads() *mockBeads {
+	return &mockBeads{
+		issues: make(map[string]*beads.Issue),
+	}
+}
+
+func (m *mockBeads) addIssue(issue *beads.Issue) {
+	m.issues[issue.ID] = issue
+}
+
+func (m *mockBeads) Show(id string) (*beads.Issue, error) {
+	if m.showFunc != nil {
+		return m.showFunc(id)
+	}
+	if issue, ok := m.issues[id]; ok {
+		return issue, nil
+	}
+	return nil, beads.ErrNotFound
+}
+
+func (m *mockBeads) List(opts beads.ListOptions) ([]*beads.Issue, error) {
+	if m.listFunc != nil {
+		return m.listFunc(opts)
+	}
+	var result []*beads.Issue
+	for _, issue := range m.issues {
+		// Apply basic filtering
+		if opts.Type != "" && issue.Type != opts.Type {
+			continue
+		}
+		if opts.Status != "" && issue.Status != opts.Status {
+			continue
+		}
+		result = append(result, issue)
+	}
+	return result, nil
+}
+
+func (m *mockBeads) Close(id string) error {
+	if m.closeFunc != nil {
+		return m.closeFunc(id)
+	}
+	if issue, ok := m.issues[id]; ok {
+		issue.Status = "closed"
+		return nil
+	}
+	return beads.ErrNotFound
+}
+
+// makeTestIssue creates a test issue with common defaults
+func makeTestIssue(id, title, issueType, status string) *beads.Issue {
+	return &beads.Issue{
+		ID:        id,
+		Title:     title,
+		Type:      issueType,
+		Status:    status,
+		Priority:  2,
+		CreatedAt: "2025-01-01T12:00:00Z",
+		UpdatedAt: "2025-01-01T12:00:00Z",
+	}
+}
+
+// makeTestMR creates a test merge request issue
+func makeTestMR(id, branch, target, worker string, status string) *beads.Issue {
+	desc := beads.FormatMRFields(&beads.MRFields{
+		Branch:      branch,
+		Target:      target,
+		Worker:      worker,
+		SourceIssue: "gt-src-123",
+		Rig:         "testrig",
+	})
+	return &beads.Issue{
+		ID:          id,
+		Title:       "Merge: " + branch,
+		Type:        "merge-request",
+		Status:      status,
+		Priority:    2,
+		Description: desc,
+		CreatedAt:   "2025-01-01T12:00:00Z",
+		UpdatedAt:   "2025-01-01T12:00:00Z",
+	}
+}