fix: silently ignore unrecognized trailing alphabetic tokens after pure numbers

[0xSoftBoi]

Summary

• GNU date accepts inputs like 8j and 8 j, treating the leading number as an hour and silently discarding the unrecognized trailing word-token. parse_datetime currently rejects these with InvalidInput.
• This PR matches GNU behavior for these cases while keeping all existing error paths intact.

Implementation

• Added Item::Noise variant for unrecognized alphabetic tokens.
• Added noise_token() as the last alternative in parse_item(), so it only fires after every other parser has already failed.
• In DateTimeBuilder::try_from, a Noise item is accepted only when it directly follows a Pure number item (prev_was_pure guard). This ensures 8j and 8 j succeed while bogus +1 day, 2025-01-01 abcdef, and NotADate still return errors.
• Added noise_after_pure_number regression test.

Test Plan

• All 134+ existing tests pass
• New regression test covers both fixed inputs and error cases

Fixes #279

[codspeed-hq]

Merging this PR will degrade performance by 11.2%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 20 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	parse_ctime_format	66.8 µs	75.2 µs	-11.2%

---

_{Comparing 0xSoftBoi:fix/ignore-trailing-noise-tokens (06267b3) with main (53ed79b)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.31%. Comparing base (7440dd9) to head (06267b3).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #286   +/-   ##
=======================================
  Coverage   99.30%   99.31%           
=======================================
  Files          20       21    +1     
  Lines        3894     3942   +48     
  Branches      122      123    +1     
=======================================
+ Hits         3867     3915   +48     
  Misses         26       26           
  Partials        1        1           

Flag	Coverage Δ
macos_latest	99.31% <100.00%> (+<0.01%)	⬆️
ubuntu_latest	99.31% <100.00%> (+<0.01%)	⬆️
windows_latest	13.95% <10.00%> (-0.10%)	⬇️

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[sylvestre]

please run cargo fmt

[tomagsx]

Review bump on this PR. I see the current blockers are the formatting failure and the CodSpeed regression flag; I can follow up on the formatting immediately, but I’d still appreciate a maintainer read on whether the GNU-compat behavior for trailing noise-after-pure-number is acceptable before this drifts.

[0xSoftBoi]

Pushed 06267b3 to address the CodSpeed regression. Instead of making Item::Noise a global alt branch, noise consumption is now folded into parse_item and only fires after a Pure item, gated on a cheap peek that confirms the next token is not a real item (timezone/offset/etc., e.g. BRT in 8 BRT).

That keeps the hot invalid-input and weekday paths byte-identical to main (no extra alt branch), so the previous -13.27% flag on parse_invalid_input should clear. All 377 tests still pass and the original noise_after_pure_number cases (8j, 8 j, 1230foo, plus the negative cases) are unchanged. cc @sylvestre