Preserve embedded comment characters in parsed INI values

[jovial-liu]

IniConfig.parse() currently truncates https://example.com/#fragment to https://example.com/ and a;b to a when stripping inline comments. This also affects continuation lines.

Treat # and ; as comment prefixes only at the start of a value or after whitespace, matching configparser with inline comment prefixes enabled. Preserve embedded delimiters, including when a later whitespace-delimited comment is present. Document the rule and update the existing no-whitespace test to reflect it.

This addresses bug 2 in #83. The malformed-section-header proposal and broader compatibility policy can be considered separately. The constructor and strip_inline_comments=False retain their existing behavior.

Validation on Python 3.12:

• Regression selection against the original parser: 15 failed, 9 passed.
• Full test suite after the fix: 78 passed.
• Ruff check and format check: passed.

Prepared with OpenAI Codex.