Bump to 0.2.0: the VAE fixes never actually shipped

The v0.1.1 tag was cut as a docs-only release two days before the VAE
rework (genuine beta-TC-VAE objective, latent-space generation/
interpolation actually producing molecules) merged to main -- so every
`pip install molgen` today gets the pre-fix code while the README
documents the post-fix behavior. Verified: a fresh 0.1.1 install has no
`vae-train`/`vae-sample`/`vae-interpolate` subcommands at all (CLI
rejects them as invalid choices), and the underlying generation code
still contains the bug the changelog already described as fixed.

This bump plus a real GitHub release is what actually gets the fix to
users; moved the changelog's `[Unreleased]` entries under a new
`[0.2.0]` heading to match.

Author: DaoyuanLi2816

CHANGELOG.md

@@ -6,6 +6,8 @@ All notable changes to this project are documented here. The format is based on
 
 ## [Unreleased]
 
+## [0.2.0]
+
 ### Changed
 - `BetaTCVAE` now optimizes a **genuine β-TC-VAE objective**: the KL term is
   decomposed into index-code mutual information, **total correlation**, and the

molgen/__init__.py

@@ -10,6 +10,6 @@
 try:
     __version__ = version("molgen")
 except PackageNotFoundError:  # pragma: no cover - running from a source checkout
-    __version__ = "0.1.1"
+    __version__ = "0.2.0"
 
 __all__ = ["__version__"]

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "molgen"
-version = "0.1.1"
+version = "0.2.0"
 description = "A lightweight toolkit for de novo molecular generation (SMILES/SELFIES; CharRNN, MolGPT, VAE)"
 readme = "README.md"
 requires-python = ">=3.9"