fix: Address golangci-lint errors (errcheck, gosec) (#76)

Apply PR #76 from dannomayernotabot:

- Add golangci exclusions for internal package false positives
- Tighten file permissions (0644 -> 0600) for sensitive files
- Add ReadHeaderTimeout to HTTP server (slowloris prevention)
- Explicit error ignoring with _ = for intentional cases
- Add //nolint comments with justifications
- Spelling: cancelled -> canceled (US locale)

Co-Authored-By: dannomayernotabot <noreply@github.com>

🤖 Generated with Claude Code

internal/cmd/town_cycle.go

@@ -15,13 +15,9 @@ import (
 var townCycleSession string
 
 // getTownLevelSessions returns the town-level session names for the current workspace.
-// Returns empty slice if workspace cannot be determined.
 func getTownLevelSessions() []string {
-	mayorSession, errMayor := getMayorSessionName()
-	deaconSession, errDeacon := getDeaconSessionName()
-	if errMayor != nil || errDeacon != nil {
-		return nil
-	}
+	mayorSession := getMayorSessionName()
+	deaconSession := getDeaconSessionName()
 	return []string{mayorSession, deaconSession}
 }
 
@@ -35,8 +31,8 @@ func isTownLevelSession(sessionName string) bool {
 	if err != nil {
 		return false
 	}
-	mayorSession, _ := getMayorSessionName()
-	deaconSession, _ := getDeaconSessionName()
+	mayorSession := getMayorSessionName()
+	deaconSession := getDeaconSessionName()
 	_ = townName // used for session name generation
 	return sessionName == mayorSession || sessionName == deaconSession
 }