feat(import): add import.orphan_handling config with 4 modes

- Add GetOrphanHandling() helper to SQLiteStorage (reads from config table)
- Add --orphan-handling flag to 'bd import' command
- Wire OrphanHandling through ImportOptions -> importer.Options
- Auto-read config if flag not provided (default: 'allow')
- Document in CONFIG.md with detailed mode explanations

Modes:
- strict: Fail on missing parent (safest)
- resurrect: Auto-create parent tombstones from JSONL
- skip: Skip orphans with warning
- allow: Import without validation (default, most permissive)

Closes bd-8072, bd-b92a

Amp-Thread-ID: https://ampcode.com/threads/T-fd18d4a5-06b3-4400-9073-194d570846d8
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/import_shared.go

@@ -158,11 +158,12 @@ func issueDataChanged(existing *types.Issue, updates map[string]interface{}) boo
 
 // ImportOptions configures how the import behaves
 type ImportOptions struct {
-	DryRun             bool // Preview changes without applying them
-	SkipUpdate         bool // Skip updating existing issues (create-only mode)
-	Strict             bool // Fail on any error (dependencies, labels, etc.)
-	RenameOnImport     bool // Rename imported issues to match database prefix
+	DryRun             bool   // Preview changes without applying them
+	SkipUpdate         bool   // Skip updating existing issues (create-only mode)
+	Strict             bool   // Fail on any error (dependencies, labels, etc.)
+	RenameOnImport     bool   // Rename imported issues to match database prefix
 	SkipPrefixValidation bool // Skip prefix validation (for auto-import)
+	OrphanHandling     string // Orphan handling mode: strict/resurrect/skip/allow (empty = use config)
 }
 
 // ImportResult contains statistics about the import operation
@@ -198,6 +199,7 @@ func importIssuesCore(ctx context.Context, dbPath string, store storage.Storage,
 		Strict:               opts.Strict,
 		RenameOnImport:       opts.RenameOnImport,
 		SkipPrefixValidation: opts.SkipPrefixValidation,
+		OrphanHandling:       importer.OrphanHandling(opts.OrphanHandling),
 	}
 
 	// Delegate to the importer package