Make InlineStr From<&T> infallible and non-panicking

[Copilot]

InlineStr had a From<&T> implementation that could panic on oversized input, violating From’s infallibility contract. This change removes that panic path and aligns behavior with other infallible InlineStr conversions.

• Problem alignment

  • Replaces fallible behavior in From<&T> (expect(...) on try_from) with an infallible conversion strategy.

• Conversion semantics

  • impl<T: AsRef<str>> From<&T> for InlineStr now:
    • copies bytes into the fixed inline buffer
    • truncates to MAX_INLINE_STR_LEN
    • never panics

• Coverage added

  • Added focused tests for oversized references converted via From<&T>:
    • &str reference path
    • &String reference path
  • Both assert truncation to inline capacity.

impl<T: AsRef<str>> From<&T> for InlineStr {
  fn from(s: &T) -> Self {
    let src = s.as_ref().as_bytes();
    let len = src.len().min(MAX_INLINE_STR_LEN);
    let mut buf = [0u8; MAX_INLINE_STR_LEN];
    buf[..len].copy_from_slice(&src[..len]);
    Self { buf, len: len as u8 }
  }
}