feat(Data/Finsupp/Weight): add degree_strictMono

[qawbecrdtey]

---

lemma degree_strictMono {R : Type*}
    [AddCommMonoid R] [PartialOrder R] [CanonicallyOrderedAdd R] [AddRightStrictMono R] :
    StrictMono (Finsupp.degree (σ := σ) (R := R))

[github-actions]

PR summary 644b02529a

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ degree_strictMono

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

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

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

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 644b025).

• +1 new declarations
• −0 removed declarations

+Finsupp.degree_strictMono

---

No changes to strong technical debt.
No changes to weak technical debt.

Current commit 644b02529a
Reference commit 54be26d06a

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.py 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).

[Ruben-VandeVelde]

AddRightStrictMono has the following comment:

You should usually not use this very granular typeclass directly, but rather a typeclass like IsOrderedAddMonoid.

I'm not sure whether this lemma falls under "usually" or not, but you should explain your thinking in the PR summary.

awaiting-author

[qawbecrdtey]

L304 uses add_lt_add_of_lt_of_le, which assumes AddRightStrictMono R. Unless there's a workaround, I guess this is reasonable.