codex: add partial c parser declarations and functions

[saidctb]

• Summary

• Added partial C parser support for simple globals, primitive typedefs, function prototypes, and function-definition signatures.
• Added top-level C source splitting that tracks braces, parentheses, brackets, strings, chars, and skips function bodies.
• Refactored c_parser/parser.py so parser internals live on CParser, matching the Fortran parser structure.
• Updated parser status from skeleton to partial across models, CLI output, tests, and docs.
• Updated C parser docs and checklist, including progress tracking: 415/848 checked (48.9%).
• Expanded focused C parser tests for declarations, functions, top-level splitting, raw conditional behavior, and macro-generated declaration deferral.

Tests

• PYTHONPATH=. pytest -q tests/parser/test_cli.py tests/parser/c
• Result: 74 passed, 62 skipped

[codecov]

Codecov Report

❌ Patch coverage is 96.05263% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
c_parser/parser.py	94.91%	1 Missing and 8 partials ⚠️

Flag	Coverage Δ
py312	92.56% <96.05%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
c_parser/lexer.py	100.00% <100.00%> (ø)
c_parser/models.py	98.75% <100.00%> (ø)
x2py/cli.py	93.41% <ø> (ø)
c_parser/parser.py	90.83% <94.91%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.