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/readers/sqlite/README.md

@@ -40,6 +40,7 @@ options := &readers.ReaderOptions{
 - Uses pure Go driver (modernc.org/sqlite) - no CGo required
 - Supports both file path and connection string
 - Auto-increment detection for INTEGER PRIMARY KEY columns
+- Generated columns (virtual and stored) are read via `PRAGMA table_xinfo`; the expression is parsed from the `CREATE TABLE` SQL
 - Foreign keys require `PRAGMA foreign_keys = ON` to be set
 
 ## Example Schema