chore(tket-qsystem): release v0.20.0

[hugrbot]

🤖 New release

• tket-qsystem: 0.19.0 -> 0.20.0 (✓ API compatible changes)

Changelog

0.20.0 - 2025-08-21

New Features

• [breaking] Update WASM extension (#1047)
• (qsystem) native gateset decomposition improvements (#1059)

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This PR was generated with release-plz.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.23%. Comparing base (126771a) to head (502ab80).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1051      +/-   ##
==========================================
+ Coverage   78.19%   78.23%   +0.03%     
==========================================
  Files         102      102              
  Lines       12783    12783              
  Branches    12504    12504              
==========================================
+ Hits         9996    10001       +5     
+ Misses       2130     2126       -4     
+ Partials      657      656       -1     

Flag	Coverage Δ
python	81.00% <ø> (ø)
rust	78.17% <ø> (+0.03%)	⬆️

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