find: -printf: don't panic on a multibyte char after an octal escape

[leeewee]

Fixes #720

find -printf '\NNN' octal escapes were parsed by slicing a fixed 3 bytes off the format string. When fewer than 3 octal digits are followed by a multibyte character (e.g. -printf '\0€'), that 3-byte slice lands inside the multibyte char and panics on a UTF-8 char-boundary assertion (exit 101); GNU find exits 0.

The octal escape is now parsed from its leading octal digits only (1 to 3, all ASCII) and the parser advances by their byte length, so a following multibyte char is never sliced into.

This also fixes \1..\7: previously only \0 was recognised and \1..\7 fell through to the single-character escape table and errored, instead of being treated as octal — now matching GNU find.

Verified byte-for-byte against GNU for \0€, \1😀, \00é, \101, \012X. Added a regression unit test.

[sylvestre]

thanks for also proposing PR !
could you please also add a test in :
tests/test_find.rs

[codspeed-hq]

Merging this PR will not alter performance

✅ 20 untouched benchmarks

---

_{Comparing leeewee:find-fix-printf-octal-escape (c705f5f) with main (865ab09)}

[codecov]

Codecov Report

❌ Patch coverage is 96.42857% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.84%. Comparing base (62deaf6) to head (c705f5f).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/find/matchers/printf.rs	96.42%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #723   +/-   ##
=======================================
  Coverage   91.83%   91.84%           
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  Files          35       35           
  Lines        7129     7149   +20     
  Branches      375      375           
=======================================
+ Hits         6547     6566   +19     
- Misses        437      438    +1     
  Partials      145      145           

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