fix(reflect): return None for string lookups on non-string maps

[Yong-yuan-X]

Summary

MapValue::get_str documents that lookups on non-string-keyed maps return None, but a debug assertion caused those calls to panic in debug builds.

Remove the assertion and retain the existing allocation-free binary search. Integer- and boolean-keyed maps now return None consistently, including through ReflectMap.

Add regression coverage for all non-string key variants and a changelog fragment.

Validation

• Confirmed the regression test fails before the fix and passes afterward.
• All 70 buffa-descriptor library tests pass with all features enabled.
• Formatting, workspace Clippy, and no_std library compilation pass.
• Workspace tests pass after skipping the existing Windows-specific systemtime_roundtrip_post_epoch failure caused by nanosecond precision loss.

[github-actions]

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[iainmcgin]

[claude code] Thanks for this. The fix is right: MapValue::get_str and ReflectMap::get_str both document None for a map that is not string-keyed, the MapView, HashMap and BTreeMap implementations already return it, and only this one panicked, in debug builds. With the assertion put back, your test fails on it; with your change, all 70 buffa-descriptor library tests pass. The comment you replaced was also wrong: the comparator is total over a mixed-key map, because every non-string variant sorts before String in MapKey's derived Ord.

I pushed one maintainer commit (bd453a4) on top:

• A second test, over a map that holds both non-string and string keys. Your test has one entry per map, so it passes whether the non-string arm returns Less or Greater; this one fails with Greater, and would fail if String stopped being MapKey's last variant.
• The .and_then after the search re-checked that the hit is a string entry. Only a string key compares Equal, so it is now a plain .map, and the comment says why.
• The changelog fragment cites (#470) and leads with the panic.