chore(Combinatorics/SimpleGraph/Copy): replace file-wide @[expose] with selective exposure

[FordUniver]

Removes the file-wide @[expose] public section and restores selective @[expose] only on the small constructive defs that need cross-module reduction: Copy.toEmbedding, Copy.id, Copy.ofLE, Copy.topEmbedding — each has an exported @[simp] lemma proved by rfl that needs the definition unfolded to typecheck. Replaces @[simps!] on topEmbedding with an explicit @[simp] topEmbedding_apply to avoid a private _proof_1 term leaking into generated lemma names; adds toEmbedding_apply to match the existing toHom_apply. Switches IsIndContained from def to abbrev so the structural alias Nonempty (G ↪g H) stays transparent, matching IsContained and Free.

Co-authored-by: Malte Jackisch 45597826+MaltyBlanket@users.noreply.github.com

---

Step 3/5 of the Copy / InducedCopy refactor-feat stack.

The noncomputable counts copyCount and unlabeledCopyCount are deliberately not exposed (see @plp127's review on #38631 explaining that unfolding a classical-Fintype.card body is rarely what you want); the downstream consumers in #38631 bridge via public *_eq_nat_card lemmas introduced in #38931 instead.

• depends on: refactor(Combinatorics/SimpleGraph/Copy): rename copy counts, align variable names, clean up docstring #38745

Diff for the changes just in this PR over its predecessor: link

[github-actions]

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[github-actions]

PR summary cb0352fd14

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ UnlabeledCopy
+ instance : FunLike (Copy G H) V W
+ instance : IsPreorder (SimpleGraph V) IsContained
+ instance : IsPreorder (SimpleGraph V) IsIndContained
+ le_card_edgeFinset_killCopies_add_unlabeledCopyCount
+ toEmbedding_apply
+ topEmbedding_apply
+ uniqueUnlabeledCopyBot
+ unlabeledCopyCount
+ unlabeledCopyCount_bot
+ unlabeledCopyCount_eq_card_image_copyToSubgraph
+ unlabeledCopyCount_eq_zero
+ unlabeledCopyCount_le_copyCount
+ unlabeledCopyCount_of_isEmpty
+ unlabeledCopyCount_pos
- copyCount_bot
- copyCount_le_labelledCopyCount
- instance : FunLike (Copy A B) α β
- instance : IsPreorder (SimpleGraph α) IsContained
- instance : IsPreorder (SimpleGraph α) IsIndContained
- le_card_edgeFinset_killCopies_add_copyCount

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 cb0352f).

• +11 new declarations
• −3 removed declarations

+SimpleGraph.Copy.toEmbedding_apply
+SimpleGraph.UnlabeledCopy
-SimpleGraph.copyCount_bot
-SimpleGraph.copyCount_le_labelledCopyCount
-SimpleGraph.le_card_edgeFinset_killCopies_add_copyCount
+SimpleGraph.le_card_edgeFinset_killCopies_add_unlabeledCopyCount
+SimpleGraph.uniqueUnlabeledCopyBot
+SimpleGraph.unlabeledCopyCount
+SimpleGraph.unlabeledCopyCount_bot
+SimpleGraph.unlabeledCopyCount_eq_card_image_copyToSubgraph
+SimpleGraph.unlabeledCopyCount_eq_zero
+SimpleGraph.unlabeledCopyCount_le_copyCount
+SimpleGraph.unlabeledCopyCount_of_isEmpty
+SimpleGraph.unlabeledCopyCount_pos

---

No changes to strong technical debt.

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

Current number	Change	Type (weak)
5012	-1	exposed public sections

Current commit cb0352fd14
Reference commit 47550252e7

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).

[mathlib-dependent-issues]

This PR/issue depends on:

• refactor(Combinatorics/SimpleGraph/Copy): rename copy counts, align variable names, clean up docstring #38745
  By Dependent Issues (🤖). Happy coding!

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[mathlib-merge-conflicts]

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[mathlib-merge-conflicts]

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