chore(Analysis/RCLike/Basic): state norm_I with positive polarity

[kim-em]

This PR restates RCLike.norm_I with the if condition in positive polarity, changing the RHS from if (I : K) ≠ 0 then 1 else 0 to if (I : K) = 0 then 0 else 1. The latter is the simp-normal form (ne_eq and ite_not rewrite the former to it) and matches every comparable if _ = 0 then 0 else 1 statement in Mathlib; the negated form was the only one of its kind. The proof is unchanged and there are no downstream uses of the lemma yet.

Follow-up to #41359 (feat(Analysis/RCLike/Basic): add norm_I).

🤖 Prepared with Claude Code

[github-actions]

PR summary 560ce3d069

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff (regex)

No declarations were harmed in the making of this PR! 🐙

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 560ce3d).

• +0 new declarations
• −0 removed declarations

No declaration differences.

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No changes to strong technical debt.

No changes to weak technical debt.

Current commit 560ce3d069
Reference commit a33a5ccd63

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.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).