feat: Handle FOREIGN KEY constraint violations gracefully during import (bd-koab)

When importing JSONL after merges that include deletions, FK constraint
violations can occur if an issue references a deleted issue. Previously,
import would fail completely. Now it continues and reports skipped dependencies.

Changes:
- Add SkippedDependencies field to Result/ImportResult structs
- Update importDependencies() to detect FK violations using IsForeignKeyConstraintError()
- Log warnings for each skipped dependency with issue IDs and type
- Continue importing remaining dependencies instead of failing
- Display summary of all skipped dependencies at end of import

Example output:
  Warning: Skipping dependency due to missing reference: bd-b → bd-a (blocks)

  ⚠️  Warning: Skipped 2 dependencies due to missing references:
    - bd-b → bd-a (blocks)
    - bd-c → bd-a (parent-child)

  This can happen after merges that delete issues referenced by other issues.
  The import continued successfully - you may want to review the skipped dependencies.

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

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

cmd/bd/import.go

@@ -366,6 +366,16 @@ NOTE: Import requires direct database access and does not work with daemon mode.
 		}
 		fmt.Fprintf(os.Stderr, "\n")
 
+		// Print skipped dependencies summary if any
+		if len(result.SkippedDependencies) > 0 {
+			fmt.Fprintf(os.Stderr, "\n⚠️  Warning: Skipped %d dependencies due to missing references:\n", len(result.SkippedDependencies))
+			for _, dep := range result.SkippedDependencies {
+				fmt.Fprintf(os.Stderr, "  - %s\n", dep)
+			}
+			fmt.Fprintf(os.Stderr, "\nThis can happen after merges that delete issues referenced by other issues.\n")
+			fmt.Fprintf(os.Stderr, "The import continued successfully - you may want to review the skipped dependencies.\n")
+		}
+
 		// Print force message if metadata was updated despite no changes
 		if force && result.Created == 0 && result.Updated == 0 && len(result.IDMapping) == 0 {
 			fmt.Fprintf(os.Stderr, "Metadata updated (database already in sync with JSONL)\n")

cmd/bd/import_shared.go

@@ -179,6 +179,7 @@ type ImportResult struct {
 	PrefixMismatch      bool              // Prefix mismatch detected
 	ExpectedPrefix      string            // Database configured prefix
 	MismatchPrefixes    map[string]int    // Map of mismatched prefixes to count
+	SkippedDependencies []string          // Dependencies skipped due to FK constraint violations
 }
 
 // importIssuesCore handles the core import logic used by both manual and auto-import.
@@ -238,6 +239,7 @@ func importIssuesCore(ctx context.Context, dbPath string, store storage.Storage,
 		PrefixMismatch:      result.PrefixMismatch,
 		ExpectedPrefix:      result.ExpectedPrefix,
 		MismatchPrefixes:    result.MismatchPrefixes,
+		SkippedDependencies: result.SkippedDependencies,
 	}, nil
 }
 

internal/importer/importer.go

@@ -50,6 +50,7 @@ type Result struct {
 	PrefixMismatch      bool              // Prefix mismatch detected
 	ExpectedPrefix      string            // Database configured prefix
 	MismatchPrefixes    map[string]int    // Map of mismatched prefixes to count
+	SkippedDependencies []string          // Dependencies skipped due to FK constraint violations
 }
 
 // ImportIssues handles the core import logic used by both manual and auto-import.
@@ -129,7 +130,7 @@ func ImportIssues(ctx context.Context, dbPath string, store storage.Storage, iss
 	}
 
 	// Import dependencies
-	if err := importDependencies(ctx, sqliteStore, issues, opts); err != nil {
+	if err := importDependencies(ctx, sqliteStore, issues, opts, result); err != nil {
 		return nil, err
 	}
 
@@ -615,7 +616,7 @@ if len(newIssues) > 0 {
 }
 
 // importDependencies imports dependency relationships
-func importDependencies(ctx context.Context, sqliteStore *sqlite.SQLiteStorage, issues []*types.Issue, opts Options) error {
+func importDependencies(ctx context.Context, sqliteStore *sqlite.SQLiteStorage, issues []*types.Issue, opts Options, result *Result) error {
 	for _, issue := range issues {
 		if len(issue.Dependencies) == 0 {
 			continue
@@ -643,6 +644,18 @@ func importDependencies(ctx context.Context, sqliteStore *sqlite.SQLiteStorage,
 
 			// Add dependency
 			if err := sqliteStore.AddDependency(ctx, dep, "import"); err != nil {
+				// Check for FOREIGN KEY constraint violation
+				if sqlite.IsForeignKeyConstraintError(err) {
+					// Log warning and track skipped dependency
+					depDesc := fmt.Sprintf("%s → %s (%s)", dep.IssueID, dep.DependsOnID, dep.Type)
+					fmt.Fprintf(os.Stderr, "Warning: Skipping dependency due to missing reference: %s\n", depDesc)
+					if result != nil {
+						result.SkippedDependencies = append(result.SkippedDependencies, depDesc)
+					}
+					continue
+				}
+
+				// For non-FK errors, respect strict mode
 				if opts.Strict {
 					return fmt.Errorf("error adding dependency %s → %s: %w", dep.IssueID, dep.DependsOnID, err)
 				}