Auto-import from git on empty DB (bd-189)

- Add checkAndAutoImport() that detects empty DB with issues in git
- Automatically imports from git HEAD:.beads/issues.jsonl
- Integrated into list, ready, and stats commands
- Zero cognitive load for agents in fresh clones
- Makes JSONL truly the source of truth
- DB becomes ephemeral cache that auto-rebuilds

Also:
- Update AGENTS.md onboarding section with import instructions
- Merge PR #98 (enhanced .gitignore)

Amp-Thread-ID: https://ampcode.com/threads/T-ffcb5e95-e5a0-486b-a0ae-ce8bd861ab9d
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/ready.go

@@ -91,10 +91,22 @@ var readyCmd = &cobra.Command{
 		ctx := context.Background()
 		issues, err := store.GetReadyWork(ctx, filter)
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
-			os.Exit(1)
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
 		}
 
+	// If no ready work found, check if git has issues and auto-import
+	if len(issues) == 0 {
+		if checkAndAutoImport(ctx, store) {
+			// Re-run the query after import
+			issues, err = store.GetReadyWork(ctx, filter)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+				os.Exit(1)
+			}
+		}
+	}
+
 		if jsonOutput {
 			// Always output array, even if empty
 			if issues == nil {
@@ -225,10 +237,22 @@ var statsCmd = &cobra.Command{
 		ctx := context.Background()
 		stats, err := store.GetStatistics(ctx)
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
-			os.Exit(1)
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
 		}
 
+	// If no issues found, check if git has issues and auto-import
+	if stats.TotalIssues == 0 {
+		if checkAndAutoImport(ctx, store) {
+			// Re-run the stats after import
+			stats, err = store.GetStatistics(ctx)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+				os.Exit(1)
+			}
+		}
+	}
+
 		if jsonOutput {
 			outputJSON(stats)
 			return