Normalize compiler paths and implementation samples in UI diagnostics

[joshlf]

Use the compiler's actual sysroot, including custom RUSTUP_HOME installations, and match it exactly so path normalization preserves neighboring diagnostic lines. Normalize rustc's arbitrary truncated implementation samples while preserving the trait header, complete lists, and specific implementation advice.

Regenerate the affected snapshots through the MSRV, stable, and nightly UI runners. Focused normalizer tests check portable samples and preservation of errors, source spans, trait names, and other advice.

Validation: official UI runners on MSRV, stable, and nightly; normalizer unit tests and nightly Clippy.
Authored by an AI agent acting on joshlf's behalf.

---

• 　  Prove record construction against independent Rust references #3744
• 　  Prove cast validation and exact metadata inference #3755
• 　  Prove byte advancement and padding sequence queries #3754
• 　  Prove normalized layout padding and field extension #3753
• 　  Prove exact trailing sizes, padding and capacity #3752
• 　  Prove primitive layout constructors with recursive mathematical models #3751
• 　  Support splitting packed DSTs through unaligned element views #3750
• 　  Compare nested DST sizes with a recursive Rust oracle #3749
• 　  Preserve nested DST padding throughout runtime layout operations #3748
• 　  Model alignment and phase encoding as a bounded mathematical pair #3747
• 　  Refine recursive record semantics into normalized layouts #3743
• 　  Prove trailing-layout normalization and capacity arithmetic #3742
• 　  Reuse Aeneas specifications for views and indexed loops #3745
• 　  Strengthen arithmetic specifications and prove arithmetic corollaries #3746
• 　  Check native total and partial Aeneas specifications #3739
• 　  Verify doc-owned specifications over recursive mathematical models #3738
• 👉 Normalize compiler paths and implementation samples in UI diagnostics #3769

Latest Update: v2 — Compare vs v1

📚 Full Patch History

Links show the diff between the row version and the column version.

Version	v1	Base
v2	vs v1	vs Base
v1		vs Base

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git fetch origin refs/heads/G5hs7ombjwaxa43hlvraivt7tlmqscvmr && git checkout -b pr-G5hs7ombjwaxa43hlvraivt7tlmqscvmr FETCH_HEAD

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[chatgpt-codex-connector]

Codex Review Summary

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

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-02T19:43:13.416445Z	7eb7f6d	PR opened
🔒 Security Review	✅ Completed 2026-10-02T19:42:51.404413Z	7eb7f6d	PR opened

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.16%. Comparing base (a2f0fa2) to head (3be4429).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3769   +/-   ##
=======================================
  Coverage   93.16%   93.16%           
=======================================
  Files          16       16           
  Lines        2413     2413           
=======================================
  Hits         2248     2248           
  Misses        165      165           

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