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/beads/agent_ids.go

@@ -1,7 +1,10 @@
 // Package beads provides a wrapper for the bd (beads) CLI.
 package beads
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 // TownBeadsPrefix is the prefix used for town-level agent beads stored in ~/gt/.beads/.
 // This distinguishes them from rig-level beads (which use project prefixes like "gt-").
@@ -74,3 +77,170 @@ func PolecatRoleBeadIDTown() string {
 func CrewRoleBeadIDTown() string {
 	return RoleBeadIDTown("crew")
 }
+
+// ===== Rig-level agent bead ID helpers (gt- prefix) =====
+
+// Agent bead ID naming convention:
+//   prefix-rig-role-name
+//
+// Examples:
+//   - gt-mayor (town-level, no rig)
+//   - gt-deacon (town-level, no rig)
+//   - gt-gastown-witness (rig-level singleton)
+//   - gt-gastown-refinery (rig-level singleton)
+//   - gt-gastown-crew-max (rig-level named agent)
+//   - gt-gastown-polecat-Toast (rig-level named agent)
+
+// AgentBeadIDWithPrefix generates an agent bead ID using the specified prefix.
+// The prefix should NOT include the hyphen (e.g., "gt", "bd", not "gt-", "bd-").
+// For town-level agents (mayor, deacon), pass empty rig and name.
+// For rig-level singletons (witness, refinery), pass empty name.
+// For named agents (crew, polecat), pass all three.
+func AgentBeadIDWithPrefix(prefix, rig, role, name string) string {
+	if rig == "" {
+		// Town-level agent: prefix-mayor, prefix-deacon
+		return prefix + "-" + role
+	}
+	if name == "" {
+		// Rig-level singleton: prefix-rig-witness, prefix-rig-refinery
+		return prefix + "-" + rig + "-" + role
+	}
+	// Rig-level named agent: prefix-rig-role-name
+	return prefix + "-" + rig + "-" + role + "-" + name
+}
+
+// AgentBeadID generates the canonical agent bead ID using "gt" prefix.
+// For non-gastown rigs, use AgentBeadIDWithPrefix with the rig's configured prefix.
+func AgentBeadID(rig, role, name string) string {
+	return AgentBeadIDWithPrefix("gt", rig, role, name)
+}
+
+// MayorBeadID returns the Mayor agent bead ID.
+//
+// Deprecated: Use MayorBeadIDTown() for town-level beads (hq- prefix).
+// This function returns "gt-mayor" which is for rig-level storage.
+// Town-level agents like Mayor should use the hq- prefix.
+func MayorBeadID() string {
+	return "gt-mayor"
+}
+
+// DeaconBeadID returns the Deacon agent bead ID.
+//
+// Deprecated: Use DeaconBeadIDTown() for town-level beads (hq- prefix).
+// This function returns "gt-deacon" which is for rig-level storage.
+// Town-level agents like Deacon should use the hq- prefix.
+func DeaconBeadID() string {
+	return "gt-deacon"
+}
+
+// DogBeadID returns a Dog agent bead ID.
+// Dogs are town-level agents, so they follow the pattern: gt-dog-<name>
+// Deprecated: Use DogBeadIDTown() for town-level beads with hq- prefix.
+// Dogs are town-level agents and should use hq-dog-<name>, not gt-dog-<name>.
+func DogBeadID(name string) string {
+	return "gt-dog-" + name
+}
+
+// WitnessBeadIDWithPrefix returns the Witness agent bead ID for a rig using the specified prefix.
+func WitnessBeadIDWithPrefix(prefix, rig string) string {
+	return AgentBeadIDWithPrefix(prefix, rig, "witness", "")
+}
+
+// WitnessBeadID returns the Witness agent bead ID for a rig using "gt" prefix.
+func WitnessBeadID(rig string) string {
+	return WitnessBeadIDWithPrefix("gt", rig)
+}
+
+// RefineryBeadIDWithPrefix returns the Refinery agent bead ID for a rig using the specified prefix.
+func RefineryBeadIDWithPrefix(prefix, rig string) string {
+	return AgentBeadIDWithPrefix(prefix, rig, "refinery", "")
+}
+
+// RefineryBeadID returns the Refinery agent bead ID for a rig using "gt" prefix.
+func RefineryBeadID(rig string) string {
+	return RefineryBeadIDWithPrefix("gt", rig)
+}
+
+// CrewBeadIDWithPrefix returns a Crew worker agent bead ID using the specified prefix.
+func CrewBeadIDWithPrefix(prefix, rig, name string) string {
+	return AgentBeadIDWithPrefix(prefix, rig, "crew", name)
+}
+
+// CrewBeadID returns a Crew worker agent bead ID using "gt" prefix.
+func CrewBeadID(rig, name string) string {
+	return CrewBeadIDWithPrefix("gt", rig, name)
+}
+
+// PolecatBeadIDWithPrefix returns a Polecat agent bead ID using the specified prefix.
+func PolecatBeadIDWithPrefix(prefix, rig, name string) string {
+	return AgentBeadIDWithPrefix(prefix, rig, "polecat", name)
+}
+
+// PolecatBeadID returns a Polecat agent bead ID using "gt" prefix.
+func PolecatBeadID(rig, name string) string {
+	return PolecatBeadIDWithPrefix("gt", rig, name)
+}
+
+// ParseAgentBeadID parses an agent bead ID into its components.
+// Returns rig, role, name, and whether parsing succeeded.
+// For town-level agents, rig will be empty.
+// For singletons, name will be empty.
+// Accepts any valid prefix (e.g., "gt-", "bd-"), not just "gt-".
+func ParseAgentBeadID(id string) (rig, role, name string, ok bool) {
+	// Find the prefix (everything before the first hyphen)
+	// Valid prefixes are 2-3 characters (e.g., "gt", "bd", "hq")
+	hyphenIdx := strings.Index(id, "-")
+	if hyphenIdx < 2 || hyphenIdx > 3 {
+		return "", "", "", false
+	}
+
+	rest := id[hyphenIdx+1:]
+	parts := strings.Split(rest, "-")
+
+	switch len(parts) {
+	case 1:
+		// Town-level: gt-mayor, bd-deacon
+		return "", parts[0], "", true
+	case 2:
+		// Could be rig-level singleton (gt-gastown-witness) or
+		// town-level named (gt-dog-alpha for dogs)
+		if parts[0] == "dog" {
+			// Dogs are town-level named agents: gt-dog-<name>
+			return "", "dog", parts[1], true
+		}
+		// Rig-level singleton: gt-gastown-witness
+		return parts[0], parts[1], "", true
+	case 3:
+		// Rig-level named: gt-gastown-crew-max, bd-beads-polecat-pearl
+		return parts[0], parts[1], parts[2], true
+	default:
+		// Handle names with hyphens: gt-gastown-polecat-my-agent-name
+		// or gt-dog-my-agent-name
+		if len(parts) >= 3 {
+			if parts[0] == "dog" {
+				// Dog with hyphenated name: gt-dog-my-dog-name
+				return "", "dog", strings.Join(parts[1:], "-"), true
+			}
+			return parts[0], parts[1], strings.Join(parts[2:], "-"), true
+		}
+		return "", "", "", false
+	}
+}
+
+// IsAgentSessionBead returns true if the bead ID represents an agent session molecule.
+// Agent session beads follow patterns like gt-mayor, bd-beads-witness, gt-gastown-crew-joe.
+// Supports any valid prefix (e.g., "gt-", "bd-"), not just "gt-".
+// These are used to track agent state and update frequently, which can create noise.
+func IsAgentSessionBead(beadID string) bool {
+	_, role, _, ok := ParseAgentBeadID(beadID)
+	if !ok {
+		return false
+	}
+	// Known agent roles
+	switch role {
+	case "mayor", "deacon", "witness", "refinery", "crew", "polecat", "dog":
+		return true
+	default:
+		return false
+	}
+}