fix: guard simulation edge cases

[galjos]

Closes #329.

• complete single-step progress without dividing by zero
• handle zero-temperature resets and velocity rescaling explicitly
• reject invalid cell-list sizes before allocation

Tests:

• testProgressbar
• testResetKinetics
• testCelllist
• testThermostat

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.83%. Comparing base (262484e) to head (a146167).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #330      +/-   ##
==========================================
+ Coverage   89.81%   89.83%   +0.02%     
==========================================
  Files         293      293              
  Lines       11420    11444      +24     
  Branches     3600     3611      +11     
==========================================
+ Hits        10257    10281      +24     
  Misses       1122     1122              
  Partials       41       41              

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[pq-perf-bot]

⚡ Performance (instruction count) — ✅ no regressions

per-benchmark breakdown

benchmark	base Ir	PR Ir	Δ
bondedForces	41.46M	41.46M	-0.00%	✅
boxTransforms	10.67M	10.67M	+0.00%	✅
constraints	11.38M	11.38M	-0.00%	✅
coulombKernel	5.80M	5.80M	+0.00%	✅
forceKernel	15.33M	15.33M	+0.00%	✅
integrator	32.17M	32.17M	-0.00%	✅
kinetics	9.53M	9.53M	+0.00%	✅
linearAlgebra	2.07M	2.07M	+0.00%	✅
nonCoulombPairs	5.48M	5.48M	-0.00%	✅
shiftVector	5.81M	5.81M	+0.00%	✅
virial	11.64M	11.63M	-0.07%	✅

_{Deterministic callgrind instruction counts vs the base branch; gated at ±2%. Not wall-clock.}

[galjos]

Superseded by focused review units: #349 for single-step progress, #350 for zero-temperature rescaling, and #348 for cell-list sizing. This combined PR should not be merged.