feat: comultiplication as a bialgebra hom

[YaelDillies]

From Toric

---

• depends on: [Merged by Bors] - feat(RingTheory): the coassoc_simps simp set #32245

[github-actions]

PR summary b43655dfe2

Import changes for modified files

Dependency changes

File	Base Count	Head Count	Change
Mathlib.RingTheory.Coalgebra.TensorProduct	1054	1056	+2 (+0.19%)

Import changes for all files

Files	Import difference
3 files Mathlib.Algebra.Category.CoalgCat.ComonEquivalence Mathlib.Algebra.Category.CoalgCat.Monoidal Mathlib.RingTheory.Coalgebra.TensorProduct	2

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Declarations diff

+ comm
+ comm_comp_comulBialgHom
+ comulBialgHom
+ comulCoalgHom

You can run this locally as follows

## summary with just the declaration names:
./scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/reporting/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[mathlib-dependent-issues]

This PR/issue depends on:

• [Merged by Bors] - feat(RingTheory): the coassoc_simps simp set #32245
  By Dependent Issues (🤖). Happy coding!

[mathlib-merge-conflicts]

This pull request has conflicts, please merge master and resolve them.