Prove normalized trailing-size and capacity formulas

[joshlf]

Give the layout implementation an independent mathematical vocabulary:
unbounded rounding, a trailing-size formula and the greatest byte capacity
within a budget.

Prove the laws needed to normalize nested rounding, shift aligned bases,
advance a formula and recognize equal size sequences. Keep alignment,
divisibility and fit assumptions explicit. These lemmas concern the
mathematics; later operation proofs connect extracted Rust to it.

Agent-authored-by: AI agent acting on joshlf's behalf

---

• 　  Prove record construction against independent Rust references #3846
• 　  Prove selected cast plans preserve size without metadata overflow #3845
• 　  Prove CastPlan selection and unchecked metadata arithmetic #3844
• 　  Prove cast validation and exact-size metadata inference #3843
• 　  Prove allocation-size preparation and tail containment #3842
• 　  Prove CastUnsized's production layout acceptance gate #3841
• 　  Prove the numerical bounds used by split operations #3840
• 　  Prove advancement and padding-sequence decisions #3839
• 　  Prove DstLayout padding and field extension #3838
• 　  Prove unit and usize PointerMetadata operations #3837
• 　  Prove trailing sizes, padding and capacity including overflow #3836
• 　  Prove primitive DstLayout constructors #3835
• 　  Add an independent Rust reference for nested DST sizes #3834
• 　  Specify rounding encodings as alignment and phase #3833
• 　  Relate recursive record layout to normalized size formulas #3832
• 👉 Prove normalized trailing-size and capacity formulas #3831
• 　  Reuse Aeneas rules for views and indexed loops #3830
• 　  Prove least padding and greatest aligned predecessors #3829
• 　  Test total and partial Aeneas contract semantics #3828
• 　  Verify Boolean and NonZeroUsize candidate predicates #3852
• 　  Verify the byte writers used by IntoBytes #3851
• 　  Prove U16 and U32 byte-order reads, writes and updates #3827
• 　  Prove guarded Boolean conversion and byte copying #3849
• 　  Reject unsupported execution effects before Aeneas lowering #3848
• 　  Check Rust specs against golden and live Aeneas models #3826
• 　  Separate cast plans from pointer reconstruction #3825
• 　  Move cast_from into layout/cast_from.rs #3824
• 　  Share Rust layout and byte models in anneal/lean #3823
• 　  Update Anneal to Aeneas ca282ec and Lean 4.31 #3822

Latest Update: v8 — Compare vs v7

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Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-08T10:22:10.055280Z	910aeeb	PR opened
🔒 Security Review	✅ Completed 2026-10-08T10:23:04.838142Z	910aeeb	PR opened

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.16%. Comparing base (d5e90be) to head (409c592).

Additional details and impacted files

@@                        Coverage Diff                         @@
##           Gfbj3enqrcenbe76pfvmdhbt2b3h3j5fj    #3831   +/-   ##
==================================================================
  Coverage                              60.16%   60.16%           
==================================================================
  Files                                     22       22           
  Lines                                   3791     3791           
==================================================================
  Hits                                    2281     2281           
  Misses                                  1510     1510           

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