feat: generated and identity columns for mssql, sqlite, drizzle, typeorm, bun and gorm readers

- mssql: write computed columns (AS (expr) PERSISTED) and identity; read computed definition and identity
- sqlite: write GENERATED ALWAYS AS (expr) STORED; read generated columns via table_xinfo and parse the expression
- drizzle: generatedAlwaysAs / generated(Always|ByDefault)AsIdentity, read and write
- typeorm: asExpression/generatedType and identity decorators, read and write; decorator scan is now quote-aware
- bun, gorm readers: read generated and identity markers
- readmes updated

pkg/writers/mssql/writer_test.go

@@ -204,3 +204,19 @@ func TestWriteComments(t *testing.T) {
 	assert.Contains(t, output, "User accounts table")
 	assert.Contains(t, output, "Primary key")
 }
+
+func TestGenerateColumnDefinition_ComputedAndIdentity(t *testing.T) {
+	writer := NewWriter(&writers.WriterOptions{})
+
+	computed := &models.Column{
+		Name:                 "full_name",
+		Type:                 "string",
+		Generated:            true,
+		GenerationExpression: "[first] + ' ' + [last]",
+		Default:              "ignored",
+	}
+	assert.Equal(t, "[full_name] AS ([first] + ' ' + [last]) PERSISTED", writer.generateColumnDefinition(computed))
+
+	identity := &models.Column{Name: "id", Type: "int", NotNull: true, Identity: true, IdentityGeneration: "ALWAYS"}
+	assert.Equal(t, "[id] INT IDENTITY(1,1) NOT NULL", writer.generateColumnDefinition(identity))
+}