bd-6xd: Standardize on issues.jsonl as canonical filename

- Change default JSONL filename from beads.jsonl to issues.jsonl
- Add bd doctor check and fix to auto-migrate legacy beads.jsonl configs
- Update FindJSONLPath to prefer issues.jsonl over beads.jsonl
- Add CheckLegacyJSONLConfig and CheckLegacyJSONLFilename checks
- Add LegacyJSONLConfig fix to rename files and update config
- Update .gitattributes to reference issues.jsonl
- Fix tests to expect new canonical filename
- Add bd-6xd to v0.25.1 release notes

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

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

internal/configfile/configfile.go

@@ -21,7 +21,7 @@ type Config struct {
 func DefaultConfig() *Config {
 	return &Config{
 		Database:    "beads.db",
-		JSONLExport: "beads.jsonl", // Default to canonical name (was issues.jsonl)
+		JSONLExport: "issues.jsonl", // Canonical name (bd-6xd)
 	}
 }
 

internal/configfile/configfile_test.go

@@ -13,9 +13,9 @@ func TestDefaultConfig(t *testing.T) {
 		t.Errorf("Database = %q, want beads.db", cfg.Database)
 	}
 
-	// bd-afd: Default changed from issues.jsonl to beads.jsonl (canonical name)
-	if cfg.JSONLExport != "beads.jsonl" {
-		t.Errorf("JSONLExport = %q, want beads.jsonl", cfg.JSONLExport)
+	// bd-6xd: issues.jsonl is the canonical name
+	if cfg.JSONLExport != "issues.jsonl" {
+		t.Errorf("JSONLExport = %q, want issues.jsonl", cfg.JSONLExport)
 	}
 }