perf: Batch and parallelize convoy worker lookups (gt-a40d8)

Optimize getWorkersForIssues() from O(N×R) to O(R) subprocess calls:
- Batch sqlite queries per rig using WHERE hook_bead IN (...)
- Parallelize rig lookups with goroutines

Expected improvement: 300-600ms → 50-100ms for moderate convoys

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

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

internal/cmd/convoy.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	tea "github.com/charmbracelet/bubbletea"
@@ -1212,64 +1213,98 @@ type workerInfo struct {
 
 // getWorkersForIssues finds workers currently assigned to the given issues.
 // Returns a map from issue ID to worker info.
+//
+// Optimized to batch queries per rig (O(R) instead of O(N×R)) and
+// parallelize across rigs.
 func getWorkersForIssues(issueIDs []string) map[string]*workerInfo {
 	result := make(map[string]*workerInfo)
 	if len(issueIDs) == 0 {
 		return result
 	}
 
-	// Query agent beads where hook_bead matches one of our issues
-	// We need to check beads across all rigs, so query each potential rig
-
 	// Find town root
 	townRoot, err := workspace.FindFromCwd()
 	if err != nil || townRoot == "" {
 		return result
 	}
 
-	// Discover rigs
+	// Discover rigs with beads databases
 	rigDirs, _ := filepath.Glob(filepath.Join(townRoot, "*", "polecats"))
+	var beadsDBS []string
 	for _, polecatsDir := range rigDirs {
 		rigDir := filepath.Dir(polecatsDir)
 		beadsDB := filepath.Join(rigDir, "mayor", "rig", ".beads", "beads.db")
-
-		// Check if beads.db exists
-		if _, err := os.Stat(beadsDB); err != nil {
-			continue
+		if _, err := os.Stat(beadsDB); err == nil {
+			beadsDBS = append(beadsDBS, beadsDB)
 		}
+	}
 
-		// Query for agent beads with matching hook_bead
-		for _, issueID := range issueIDs {
-			if _, ok := result[issueID]; ok {
-				continue // Already found a worker for this issue
-			}
+	if len(beadsDBS) == 0 {
+		return result
+	}
 
-			// Query for agent bead with this hook_bead
-			safeID := strings.ReplaceAll(issueID, "'", "''")
-			query := fmt.Sprintf(
-				`SELECT id, hook_bead, last_activity FROM issues WHERE issue_type = 'agent' AND status = 'open' AND hook_bead = '%s' LIMIT 1`,
-				safeID)
+	// Build the IN clause with properly escaped issue IDs
+	var quotedIDs []string
+	for _, id := range issueIDs {
+		safeID := strings.ReplaceAll(id, "'", "''")
+		quotedIDs = append(quotedIDs, fmt.Sprintf("'%s'", safeID))
+	}
+	inClause := strings.Join(quotedIDs, ", ")
 
-			queryCmd := exec.Command("sqlite3", "-json", beadsDB, query)
+	// Batch query: fetch all matching agents in one query per rig
+	query := fmt.Sprintf(
+		`SELECT id, hook_bead, last_activity FROM issues WHERE issue_type = 'agent' AND status = 'open' AND hook_bead IN (%s)`,
+		inClause)
+
+	// Query all rigs in parallel
+	type rigResult struct {
+		agents []struct {
+			ID           string `json:"id"`
+			HookBead     string `json:"hook_bead"`
+			LastActivity string `json:"last_activity"`
+		}
+	}
+
+	resultChan := make(chan rigResult, len(beadsDBS))
+	var wg sync.WaitGroup
+
+	for _, beadsDB := range beadsDBS {
+		wg.Add(1)
+		go func(db string) {
+			defer wg.Done()
+
+			queryCmd := exec.Command("sqlite3", "-json", db, query)
 			var stdout bytes.Buffer
 			queryCmd.Stdout = &stdout
 			if err := queryCmd.Run(); err != nil {
-				continue
+				resultChan <- rigResult{}
+				return
 			}
 
-			var agents []struct {
-				ID           string `json:"id"`
-				HookBead     string `json:"hook_bead"`
-				LastActivity string `json:"last_activity"`
+			var rr rigResult
+			if err := json.Unmarshal(stdout.Bytes(), &rr.agents); err != nil {
+				resultChan <- rigResult{}
+				return
 			}
-			if err := json.Unmarshal(stdout.Bytes(), &agents); err != nil || len(agents) == 0 {
+			resultChan <- rr
+		}(beadsDB)
+	}
+
+	// Wait for all queries to complete
+	go func() {
+		wg.Wait()
+		close(resultChan)
+	}()
+
+	// Collect results from all rigs
+	for rr := range resultChan {
+		for _, agent := range rr.agents {
+			// Skip if we already found a worker for this issue
+			if _, ok := result[agent.HookBead]; ok {
 				continue
 			}
 
-			agent := agents[0]
-
 			// Parse agent ID to get worker identity
-			// Format: gt-<rig>-<role>-<name> or gt-<rig>-<name>
 			workerID := parseWorkerFromAgentBead(agent.ID)
 			if workerID == "" {
 				continue
@@ -1283,7 +1318,7 @@ func getWorkersForIssues(issueIDs []string) map[string]*workerInfo {
 				}
 			}
 
-			result[issueID] = &workerInfo{
+			result[agent.HookBead] = &workerInfo{
 				Worker: workerID,
 				Age:    age,
 			}