feat: identifying WithZero (Multiplicative M) and WithTop M

[WilliamCoram]

We identify Mᵐ⁰ = WithZero (Multiplicative M) with WithTop M in the form of the order-and-additive isomorphism.

In future work this will allow us to define additive valuations from valuations with a usable target (specifically attaching to a rank one discrete valuation an additive valuation into WithTop Z).

AI usage:
The need of attaching additive valuations to valuations came up in my Newton polygon work - after some discussion with people and Claude this was the approach I felt worked best for me. The file was drafted and written by Claude with my input and cleaning.

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[github-actions]

PR summary c2a17f4dd6

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Algebra.Order.GroupWithZero.NegLog (new file)	552

---

Declarations diff (regex)

+ mapAddHom'
+ mapAddHom'_exp
+ mapAddHom'_strictMono
+ negLog
+ negLog_eq_coe
+ negLog_eq_top
+ negLog_exp
+ negLog_le_negLog
+ negLog_mapAddHom'
+ negLog_mul
+ negLog_one
+ negLog_zero
+ orderAddIsoWithTop
+ orderAddIsoWithTop_apply

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 c2a17f4).

• +14 new declarations
• −0 removed declarations

+WithZero.mapAddHom'
+WithZero.mapAddHom'_exp
+WithZero.mapAddHom'_strictMono
+WithZero.negLog
+WithZero.negLog_eq_coe
+WithZero.negLog_eq_top
+WithZero.negLog_exp
+WithZero.negLog_le_negLog
+WithZero.negLog_mapAddHom'
+WithZero.negLog_mul
+WithZero.negLog_one
+WithZero.negLog_zero
+WithZero.orderAddIsoWithTop
+WithZero.orderAddIsoWithTop_apply

---

No changes to strong technical debt.

Increase in weak tech debt: (relative, absolute) = (1.00, 0.00)

Current number	Change	Type (weak)
exposed public sections	5062	1

Current commit c2a17f4dd6
Reference commit 98b840bb29

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).