[ashishsoni-ai]

Closes #176

Summary

This PR addresses issue #176 by enforcing validation of the evolution method configuration in write_operator_card:

1. Raise error when iterations > 1 for truncated evolution (src/pineko/evolve.py):

   • Truncated evolution (ModEv == "TRN") does not support breaking the evolution integral into multiple iterations (IterEv > 1). Previously, any IterEv > 1 was silently ignored and overwritten with 1.
   • Now explicitly raises ValueError if tcard["ModEv"] == "TRN" and IterEv > 1, as requested by @scarlehoff in Raise an error when the number of iterations > 1 for truncated #176.

2. Fix literal comparison bug:

   • Corrected line 330 where if "IterEv" not in tcard and "ModEv" == "EXA": compared the string literal "ModEv" to "EXA", leaving the IterEv presence check for exact evolution dead. Changed to tcard["ModEv"] == "EXA".

3. Guards for unsupported evolution methods:

   • Added an explicit else branch raising ValueError if tcard["ModEv"] is not recognized, preventing incomplete operator card generation.

4. Unit Tests (tests/test_evolve.py):

   • Added test_write_operator_card_evolution_methods using the FakePine mock to verify:
     • Missing ModEv raises ValueError.
     • Unknown ModEv raises ValueError.
     • ModEv == "EXA" without IterEv raises ValueError.
     • ModEv == "EXA" with IterEv succeeds.
     • ModEv == "TRN" with IterEv > 1 raises ValueError.
     • ModEv == "TRN" with IterEv == 1 succeeds.

Verification

• Tested locally with pytest tests/test_evolve.py: 2 passed (100%).
• Formatted with black: 0 issues.
• git diff --check: 0 issues.