Give PySB import the same reserved-name rename-and-restore as SBML

[dweindl]

A model quantity literally named one of AMICI's reserved array-parameter
names (t, x, p, k, h, w, y) used to hit a hard ValueError on PySB/BNGL
import, since only SbmlImporter renamed and restored these names before
embedding them anywhere. This applies the same rename-and-restore at
PySB's own symbol-minting sites (parameters, expressions/observables, and
the stoichiometric matrix's derivative computation), sharing the
disambiguation logic with SBML via a new resolve_reserved_symbol_renames
helper.

• Drops the test_pysb_event "kk" workaround.
• Drops the empty_compartments_block/motor BNGL expected-failure
  special case -- both now import and simulate successfully.
• Adds a dedicated regression test (test_pysb_reserved_names).

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 93.93939% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.94%. Comparing base (9b17bdd) to head (2a5582a).

Files with missing lines	Patch %	Lines
python/sdist/amici/importers/utils.py	86.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3243      +/-   ##
==========================================
- Coverage   78.32%   77.94%   -0.38%     
==========================================
  Files         318      318              
  Lines       22183    22193      +10     
  Branches     1490     1490              
==========================================
- Hits        17374    17298      -76     
- Misses       4801     4887      +86     
  Partials        8        8              

Flag	Coverage Δ
cpp	72.29% <90.90%> (-0.02%)	⬇️
cpp_python	35.03% <87.87%> (+0.04%)	⬆️
petab	48.10% <93.93%> (+0.02%)	⬆️
petab_sciml	16.30% <33.33%> (+0.01%)	⬆️
petab_sciml_benchmarks	14.88% <33.33%> (+0.01%)	⬆️
python	70.74% <90.90%> (-0.02%)	⬇️
sbmlsuite-jax	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
python/sdist/amici/importers/pysb/__init__.py	94.62% <100.00%> (+0.04%)	⬆️
python/sdist/amici/importers/sbml/__init__.py	83.17% <100.00%> (-6.86%)	⬇️
python/sdist/amici/importers/utils.py	83.33% <86.66%> (-1.67%)	⬇️

... and 3 files with indirect coverage changes

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