Fix SPMe Surface Form Discrepancy

[vidipsingh]

Description

This PR resolves the mismatch between surface form = "false" and algebraic in SPMe for single-phase configs, ensuring consistent results. It also improves validation for particle phases = ("1", "1") to avoid unintended overrides.

Fixes: #4910

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #)

Important checks:

Please confirm the following before marking the PR as ready for review:

• No style issues: nox -s pre-commit
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• The documentation builds: nox -s doctests
• Code is commented for hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[vidipsingh]

Hi @valentinsulzer, I've made these changes:

• Ensured surface form = "false" and "algebraic" match for single-phase SPMe ("particle phases": ("1", "1")) by using delta_phi = phi_s - phi_e in CompositeAlgebraic, with validation, and logging.
• Fixed the particle phases override bug by defaulting to "false" for single-phase setups.

Is this approach correct? Any feedback would be very helpful!

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.54839% with 2 lines in your changes missing coverage. Please review.

Project coverage is 99.11%. Comparing base (1ce4ef2) to head (90a4cb7). Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
...amm/models/full_battery_models/lithium_ion/spme.py	87.50%	2 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4986      +/-   ##
===========================================
- Coverage    99.12%   99.11%   -0.01%     
===========================================
  Files          304      305       +1     
  Lines        23576    23637      +61     
===========================================
+ Hits         23369    23428      +59     
- Misses         207      209       +2     

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