refactor(beads,mail): split large files into focused modules

Break down monolithic beads.go and mail.go into smaller, single-purpose files:

beads package:
- beads_agent.go: Agent-related bead operations
- beads_delegation.go: Delegation bead handling
- beads_dog.go: Dog pool operations
- beads_merge_slot.go: Merge slot management
- beads_mr.go: Merge request operations
- beads_redirect.go: Redirect bead handling
- beads_rig.go: Rig bead operations
- beads_role.go: Role bead management

cmd package:
- mail_announce.go: Announcement subcommand
- mail_check.go: Mail check subcommand
- mail_identity.go: Identity management
- mail_inbox.go: Inbox operations
- mail_queue.go: Queue subcommand
- mail_search.go: Search functionality
- mail_send.go: Send subcommand
- mail_thread.go: Thread operations

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

internal/cmd/mail_search.go

@@ -0,0 +1,90 @@
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+	"github.com/steveyegge/gastown/internal/mail"
+	"github.com/steveyegge/gastown/internal/style"
+)
+
+// runMailSearch searches for messages matching a pattern.
+func runMailSearch(cmd *cobra.Command, args []string) error {
+	query := args[0]
+
+	// Determine which inbox to search
+	address := detectSender()
+
+	// Get workspace for mail operations
+	workDir, err := findMailWorkDir()
+	if err != nil {
+		return fmt.Errorf("not in a Gas Town workspace: %w", err)
+	}
+
+	// Get mailbox
+	router := mail.NewRouter(workDir)
+	mailbox, err := router.GetMailbox(address)
+	if err != nil {
+		return fmt.Errorf("getting mailbox: %w", err)
+	}
+
+	// Build search options
+	opts := mail.SearchOptions{
+		Query:       query,
+		FromFilter:  mailSearchFrom,
+		SubjectOnly: mailSearchSubject,
+		BodyOnly:    mailSearchBody,
+	}
+
+	// Execute search
+	messages, err := mailbox.Search(opts)
+	if err != nil {
+		return fmt.Errorf("searching messages: %w", err)
+	}
+
+	// JSON output
+	if mailSearchJSON {
+		enc := json.NewEncoder(os.Stdout)
+		enc.SetIndent("", "  ")
+		return enc.Encode(messages)
+	}
+
+	// Human-readable output
+	fmt.Printf("%s Search results for %s: %d message(s)\n\n",
+		style.Bold.Render("🔍"), address, len(messages))
+
+	if len(messages) == 0 {
+		fmt.Printf("  %s\n", style.Dim.Render("(no matches)"))
+		return nil
+	}
+
+	for _, msg := range messages {
+		readMarker := "●"
+		if msg.Read {
+			readMarker = "○"
+		}
+		typeMarker := ""
+		if msg.Type != "" && msg.Type != mail.TypeNotification {
+			typeMarker = fmt.Sprintf(" [%s]", msg.Type)
+		}
+		priorityMarker := ""
+		if msg.Priority == mail.PriorityHigh || msg.Priority == mail.PriorityUrgent {
+			priorityMarker = " " + style.Bold.Render("!")
+		}
+		wispMarker := ""
+		if msg.Wisp {
+			wispMarker = " " + style.Dim.Render("(wisp)")
+		}
+
+		fmt.Printf("  %s %s%s%s%s\n", readMarker, msg.Subject, typeMarker, priorityMarker, wispMarker)
+		fmt.Printf("    %s from %s\n",
+			style.Dim.Render(msg.ID),
+			msg.From)
+		fmt.Printf("    %s\n",
+			style.Dim.Render(msg.Timestamp.Format("2006-01-02 15:04")))
+	}
+
+	return nil
+}