Replay the Erdős 828 totient-divisibility classification

[DomTheDeveloper]

Green result

The exact historical proof now compiles against the current Erdős 828 definitions and pinned Lean toolchain.

It proves the full classification:

φ n ∣ n ↔ n ≤ 1 ∨ ∃ᵉ (a > 0) (b), n = 2 ^ a * 3 ^ b

using strong induction, the parity of Euler's totient, prime-power factorization, and the two-prime obstruction.

Immutable provenance

• Historical source blob: c1ebc4e74a2308c13aa72ce65fa3ea5a172c127e
• Audit branch head: 59604dd67b7a3c7d1eb7f328dac2dbe70cfbf10e
• Focused run: 30214195665

The run passed current catalog-module build, exact theorem extraction, no-hole/no-trust scan, complete compilation, and exact theorem axiom inspection.

Axiom footprint:

[propext, Classical.choice, Quot.sound]

No sorryAx or compiler-trust dependency appears.

Status

Green proof recovery. The current admitted textbook declaration still needs a focused restoration/style-cleanup patch before promotion to _PRs/ready/. This audit-only PR should not merge.

[github-actions]

👋 This is an automated welcome message. 🤖
Thanks for the contributions!

A few friendly reminders while the review gets started:

• Please take a look at the style guidelines,
  especially the conventions for references, categories, AMS tags, and answer(sorry).
• You can manage some PR labels by leaving a comment with +label-name or -label-name; for example, +awaiting-author or -awaiting-author.
• This repository is mainly for formalised statements. Proofs longer than about 25-50 lines are usually out of scope; longer proofs are welcome to be included/linked via the formal_proof mechanism.

Thanks again for helping improve Formal Conjectures.