[codex] Refactor plugin SQL builders

[datlechin]

Summary

• Centralize plugin SQL dialect quoting, literal escaping, filter query assembly, and DML statement generation helpers.
• Add shared PluginSQLDDLBuilder helpers for column definitions, default values, indexes, foreign keys, primary keys, and ALTER TABLE column operations.
• Refactor SQL driver plugins to use the shared builders while preserving dialect-specific behavior for SQLite, LibSQL, D1, ClickHouse, PostgreSQL, DuckDB, Oracle, MySQL, MSSQL, BigQuery, and Cassandra.
• Add focused SQLDialectDescriptorTests coverage for the new shared SQL builder behavior.

Validation

• git diff --check HEAD^..HEAD
• Clean worktree build: xcodebuild build -project TablePro.xcodeproj -target TableProPluginKit -destination 'platform=macOS' -skipPackagePluginValidation -quiet
• Clean worktree targeted test: xcodebuild test -project TablePro.xcodeproj -scheme TablePro -destination 'platform=macOS' -only-testing:TableProTests/SQLDialectDescriptorTests -skipPackagePluginValidation -derivedDataPath /tmp/TableProCodexDerivedData-PluginDDLPR-FinalNoSign -quiet CODE_SIGNING_ALLOWED=NO

Notes

• Local clean test setup required a gitignored Secrets.xcconfig placeholder and local Libs/ static libraries, matching the repository setup docs.
• Existing SwiftLint, Swift concurrency, linker, and asset catalog warnings are still present and unrelated to this PR.