chore: remove legacy / unused code in core

[AyushAgrawal-A2]

No description provided.

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✅ Deploy images - Sep 30, 2025 at 03:43 PM UTC - Preview
✅ Tests-E2E - Report

[codecov]

Codecov Report

❌ Patch coverage is 94.03153% with 106 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.03%. Comparing base (de85dc1) to head (e9a6804).

Files with missing lines	Patch %	Lines
...uadratic-core/src/controller/operations/borders.rs	36.36%	28 Missing ⚠️
...roller/active_transactions/unsaved_transactions.rs	36.00%	16 Missing ⚠️
quadratic-core/src/grid/block/mod.rs	62.50%	6 Missing ⚠️
quadratic-core/src/controller/transaction.rs	54.54%	5 Missing ⚠️
quadratic-core/src/a1/a1_selection/query.rs	95.52%	3 Missing ⚠️
...dratic-core/src/controller/user_actions/offsets.rs	25.00%	3 Missing ⚠️
quadratic-core/src/grid/formatting.rs	40.00%	3 Missing ⚠️
quadratic-core/src/grid/sheet/data_tables/cache.rs	90.90%	3 Missing ⚠️
quadratic-core/src/a1/a1_selection/mutate.rs	94.11%	2 Missing ⚠️
quadratic-core/src/a1/cell_ref_end.rs	89.47%	2 Missing ⚠️
... and 29 more

Additional details and impacted files

@@                    Coverage Diff                     @@
##           remove-code-cell-value    #3485      +/-   ##
==========================================================
+ Coverage                   89.67%   90.03%   +0.35%     
==========================================================
  Files                         437      435       -2     
  Lines                       89463    85905    -3558     
==========================================================
- Hits                        80228    77341    -2887     
+ Misses                       9235     8564     -671     

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