feat(dbml): @postgres/@sqlite dialect directives (#19)

Add parseable `@<namespace>[(<target>)]: <args>` directives embedded in DBML.
They are stored losslessly on each object's Metadata, round-trip unchanged
through the DBML writer, and are translated to SQL only by the writer for the
matching dialect.

- models: Directive type + catalog; Metadata map added to Column and Index
- dbml reader: parse and attach directives at database/table/column/index
  level; line-numbered errors; repeatable by default with singleton duplicate
  detection. Fixes a preexisting bug where an `indexes {}` closing brace ended
  the table early, dropping trailing Note: and directive lines.
- dbml writer: re-emit directives at their location; idempotent output
- pgsql writer: PARTITION BY / INHERITS / WITH / TABLESPACE (table),
  STORAGE / COMPRESSION / identity (column), WITH / TABLESPACE (index)
- sqlite writer: WITHOUT ROWID / STRICT (table), COLLATE (column)
- --strict-directives flag on ReaderOptions and WriterOptions
- docs/DBML_DIRECTIVES.md + reader/writer READMEs

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ss2MY5J11cRGwEz86ZXk7d

cmd/relspec/prisma_options.go

@@ -10,17 +10,19 @@ func newReaderOptions(filePath, connString string) *readers.ReaderOptions {
 		FilePath:         filePath,
 		ConnectionString: connString,
 		Prisma7:          prisma7,
+		StrictDirectives: strictDirectives,
 	}
 }
 
 func newWriterOptions(outputPath, packageName string, flattenSchema bool, nullableTypes, nullableArrays string, continueOnError bool) *writers.WriterOptions {
 	return &writers.WriterOptions{
-		OutputPath:      outputPath,
-		PackageName:     packageName,
-		FlattenSchema:   flattenSchema,
-		NullableTypes:   nullableTypes,
-		NullableArrays:  nullableArrays,
-		Prisma7:         prisma7,
-		ContinueOnError: continueOnError,
+		OutputPath:       outputPath,
+		PackageName:      packageName,
+		FlattenSchema:    flattenSchema,
+		NullableTypes:    nullableTypes,
+		NullableArrays:   nullableArrays,
+		Prisma7:          prisma7,
+		ContinueOnError:  continueOnError,
+		StrictDirectives: strictDirectives,
 	}
 }

cmd/relspec/root.go

@@ -10,10 +10,11 @@ import (
 
 var (
 	// Version information, set via ldflags during build
-	version   = "dev"
-	buildDate = "unknown"
-	prisma7   bool
-	noVersion bool
+	version          = "dev"
+	buildDate        = "unknown"
+	prisma7          bool
+	noVersion        bool
+	strictDirectives bool
 )
 
 func init() {
@@ -72,6 +73,7 @@ func init() {
 	rootCmd.AddCommand(reportCmd)
 	rootCmd.PersistentFlags().BoolVar(&prisma7, "prisma7", false, "Use Prisma 7 generator conventions when reading/writing Prisma schemas")
 	rootCmd.PersistentFlags().BoolVar(&noVersion, "no-version", false, "Suppress the RelSpec version header")
+	rootCmd.PersistentFlags().BoolVar(&strictDirectives, "strict-directives", false, "Fail on unknown or untranslatable DBML dialect directives (@postgres:, @sqlite:, …)")
 }
 
 // printVersionHeader prints the "RelSpec <version> (built: <date>)" banner