Fix failing ci docs

[ShantanuKodgirwar]

What and why

Fixes the failing docs deploy and adds a docs check to PRs so failures like this show up before merging.

• Broken API reference: docs/api/engines.md still pointed at PtyLab.Engines.pcPIE, which was deleted in 81d1127. It now points at PtyLab.Engines.mPIE.pcPIE, the deprecated wrapper. The position-correction and engine guides now say to use mPIE with params.positionCorrectionSwitch = True.
• Docstring warnings: Google-style Returns: entries such as tuple: were read by griffe as names, not types, which gave 13 warnings that fail --strict. Added returns_named_value: false to the mkdocstrings options in mkdocs.yml.
• Deprecation warning on import: the pcPIE warning was raised on every import PtyLab.Engines. It now fires only when a pcPIE is created.
• Escape sequence: fixed the invalid \m escape in TensorboardMonitor.py by making the string a raw f-string.
• Docs CI: split docs.yml into a build job that also runs on PRs and a deploy job that runs only on main. Pages write permissions now apply only to deploy.
• README: removed pcPIE from the feature list and added a Docs status badge that links to the docs site.
• Version: bumped from 0.3.2 to 0.3.3.

How it was tested

• uv run --extra docs mkdocs build --strict passes locally with no warnings.
• import PtyLab.Engines no longer raises the deprecation warning. Creating Engines.pcPIE(...) raises it, pointing at the caller's line.

Notes

• After merging, add Docs / build as a required status check on main so a failing docs build blocks merges.
• example_scripts/exampleReconstruction_pcPIE.py and the lateral position correction tutorial notebook still use Engines.pcPIE. They still work but now show the deprecation warning; they can be moved to mPIE in a follow-up.
• No change to reconstruction results.