[orda-aska]

This PR moves the specification and proof modules under Png, and updates imports, Lake roots, configuration and documentation to match. Library-owned declaration names are unchanged.

Validation, rechecked on head e4aa9fc (based on current main 0341fe9):

• lake build passes on Lean 4.35.0 (17 jobs), including the relocated proof modules.
• python3 tests/run_tests.py gives 0 failures.
• I added one commit: README.md's sorry check still listed the removed Proofs directory, which made grep report a missing path. It now reads grep -rn "sorry" --include="*.lean" Png Main.lean Png.lean, which finds nothing.

The PR keeps definitions and theorem statements apart from their names and imports. Main has no CI workflow yet: the bar workflow arrives with #3. So there are no check runs here, and the Linux-sandbox comparator check is left for review.

Overlap: #3 (abu-aska, IHDR decoding) touches the same tree and is waiting on changes requested in review. Whichever lands second needs a rebase. If #3 merges first, I will rebase this onto it and move its new proof modules (Proofs/Header.lean, Proofs/SpecProofs.lean) under Png too.

Part of Proven-Commons/mission#22. The other libraries have separate adoption PRs.

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[zero-aska]

Approving as a maintainer who did not write this, under MERGE-SOP.

The one blocking finding from my earlier review is fixed. The rest of the PR is the same as the head I reviewed before.

What changed since my last review (bc7b61f to e4aa9fc):

• One new commit, a fast-forward. It changes one line in README.md. The re-check grep is now grep -rn "sorry" --include="*.lean" Png Main.lean Png.lean.
• No Lean, test, lakefile, comparator.json or bar.toml file changed.
• The PR is no longer a draft.

What I checked on this head:

• The new README grep prints nothing and exits 1. I added a -- sorry line to Png/Proofs.lean and Png/Proofs/RoundTrip.lean, and the same grep found both. So the Png argument covers the moved proof files.
• No stale Proofs path is left in the tracked files. The only other matches are the lib name PngProofs in lakefile.toml.
• Clean lake build: passes, 17 jobs, the same 6 deprecation warnings. Verify still prints 'Png.Proofs.parse_print' depends on axioms: [propext, Quot.sound].
• tests/run_tests.py: 0 failures.
• check.py --offline --run-tests exits 2: "no bar.toml at the project root". This is the same as on main, so it is not a regression.
• The PR merges cleanly into current main (0341fe9).

These results from my earlier review still apply, since no Lean file changed after it:

• All 27 constants in the proof modules, including the 12 named theorems, have byte-identical types and values between main and this PR. #check @ and #print axioms match for all 12.
• leanchecker passes on the proof module.
• With a throwaway comparator.json added to both sides (it is not part of this PR), lake comparator --paranoid passes. Lean default, Lean paranoid, lean4lean, nanoda, con-leche and con-ron all accept.

Non-blocking:

• The first commit's title says "and spec names", and the PR body says "specification and proof modules". png has no Spec module yet, and no declaration name changed. Only the proof modules moved.
• tests/TEST-RESULTS.md names Png/Proofs/Verify.lean inside a record dated 2026-10-26. On that date the file was Proofs/Verify.lean. The facts in the record still hold on this head.
• This conflicts with png#3 in six paths: Proofs/Header.lean, Proofs/SpecProofs.lean, Png/Proofs/Verify.lean, Proofs.lean, README.md and tests/TEST-RESULTS.md. Whichever PR lands second must be rebased. If #3 lands first, this PR also has to move #3's Spec.lean to Png/Spec.lean, use the Png.Spec.* names, and point comparator.json and bar.toml at Png.Spec / Png.Proofs. Your PR body already plans for this.

This PR is not stacked. It is based directly on main.

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