feat: implement PLEXOS solution reader and setup master files for 9-12 versions

[mcllerena]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.63978% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.00%. Comparing base (3003e52) to head (11f9283).

Files with missing lines	Patch %	Lines
src/plexosdb/db.py	87.62%	12 Missing ⚠️
src/plexosdb/solution_reader/_materialize.py	98.21%	5 Missing ⚠️
src/plexosdb/solution_reader/_bin_decode.py	96.36%	4 Missing ⚠️
src/plexosdb/solution_reader/_xml_import.py	92.85%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
+ Coverage   95.55%   96.00%   +0.44%     
==========================================
  Files           8       15       +7     
  Lines        1823     2527     +704     
==========================================
+ Hits         1742     2426     +684     
- Misses         81      101      +20     

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[mcllerena]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts have been resolved in commit 0c97e00.

The key resolutions were:

• db.py: Fixed PROPERTY_QUERY path to use plexosdb.sql (correct), merged create_schema to support both versioned master template loading (int/tuple/v-string) from this PR and config-only string version updates + seed_defaults from main, added _seed_default_model_data from main
• docs/source/howtos/create_db.md and docs/source/tutorial.md: Combined documentation from both branches covering all features

All 892 tests pass.

[pesap]

Two notes could not be attached inline because GitHub reports the XML diffs are too large for inline review comments:

1. src/plexosdb/config/master_9.2R6_btu.xml has trailing whitespace/line-ending noise from the first line onward. Please normalize the generated template files, or explicitly exclude them from the whitespace check if preserving source formatting is intentional.
2. The raw src/plexosdb/config/master_*.xml templates add roughly 28 MB / 820k lines of package data. Since runtime loads them through importlib.resources, please verify the built wheel/sdist includes them intentionally and that the package-size increase is acceptable.