[driade]

Python 3.14 reports invalid string escapes and a return inside finally when the Sublime plugin loads. Use raw strings and return after restoring the editor setting. Also fix MergeException message access so rollback restores the original buffer instead of silently leaving a partial edit.

Add 11 standard-library tests covering source compilation, completion escaping, patch headers, buffer edits and exception recovery. Keep the test harness compatible with Python 3.3 and preserve real imported dependencies while isolating the Sublime API.

The regular CI suite tests all nine combinations of Python 3.3, 3.8 and 3.14 with Linux, macOS Intel and Windows. Each job verifies its actual interpreter before compiling the plugin and running the same tests. Legacy Python 3.3 is built from the official 3.3.7 sources on Linux and uses the official 3.3.5 binaries on macOS/Windows; the macOS framework is extracted into the temporary runner directory without system installation.

Add four integration tests inside official stable Sublime Text 4200 in evaluation mode, without a license or repository secrets. Run Python hosts 3.3 and 3.8 on Linux, macOS Intel and Windows. Reuse pinned UnitTesting 1.9.2 and retain editor logs as CI artifacts. Tests cover loading, formatting and idempotence, real PHP/SQLite completion snippets, and rollback on a real buffer.

The editor tests also exposed a completion regression: modern PHP syntax uses source.php.embedded.html. Use Sublime match_selector instead of exact historical scope names.

Validation:

• Real Sublime CI: all six combinations pass (4 tests each), without a license: https://github.com/driade/phpfmt8/actions/runs/37903820198.
• Python CI: all nine combinations pass (11 tests each): https://github.com/driade/phpfmt8/actions/runs/37903820179.
• Python 3.14.7 and 3.11.16: 11 local tests pass.
• PHPUnit 11.5.57 on PHP 8.2.33: 48 tests, 48 assertions pass.
• PHP fixture suite: 604 cases, Broken:0 on PHP 8.2 and 7.4, with version-dependent skips.
• The installed Sublime build 4200 only bundles Python 3.3/3.8. Real-editor validation with Python 3.14 remains pending.

Refs #102. Plane: PHPFMT-2.