Fix Io_Implied_Do rejecting a minimal-length io-implied-do (closes #524)

[DisciplinedSoftware]

Closes #524.

The length guard in Io_Implied_Do.match used <= 9, but the shortest legal io-implied-do, e.g. (i,i=1,n), is exactly 9 characters, so statements such as WRITE (IOUT,10) N,(I,I=1,J) failed to parse (found while parsing MODFLOW-2005, gwf2swr7.f:4074). The guard is changed to < 9 and a minimal-length case is added to test_io_implied_do.

• pytest src/fparser passes (2950 passed, 24 xfailed, 1 pre-existing xpassed)
• black clean
• CHANGELOG.md updated (the PR-number placeholder will be filled in once this PR's number is known)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This pull request fixes an off-by-one length check in Io_Implied_Do.match that incorrectly rejected the shortest valid io-implied-do form (9 characters, e.g. (i,i=1,n)), causing valid WRITE statements to fail to parse (as reported in issue #524).

Changes:

• Adjust Io_Implied_Do.match guard from len(string) <= 9 to len(string) < 9 to allow minimal-length io-implied-do constructs.
• Add a regression test covering the 9-character minimal-length case in test_io_implied_do.
• Add a corresponding entry to CHANGELOG.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/fparser/two/Fortran2003.py	Fixes the io-implied-do length guard off-by-one so minimal valid constructs are accepted.
src/fparser/two/tests/test_fortran2003.py	Adds a regression test for a minimal-length io-implied-do string.
CHANGELOG.md	Records the bugfix and references the associated issue/PR.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.25%. Comparing base (18ff788) to head (59c0e2d).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #525   +/-   ##
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  Coverage   92.25%   92.25%           
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  Files          89       89           
  Lines       13891    13891           
=======================================
  Hits        12815    12815           
  Misses       1076     1076           

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[arporter]

All looks good, thanks very much @DisciplinedSoftware.
Please note that it is the code reviewer who updates the changelog as that's the last thing that must be done before the final merge. We get conflicts otherwise.