[path_parsing] Add documentation for public API members in path_parsing

[mozammal-hossain]

Adds comprehensive documentation for all public API members in the path_parsing
package, addressing the TODO to remove the public_member_api_docs lint ignore.

What changed:

• Added dartdoc comments for all public classes, methods, and properties
• Documented PathProxy interface (moveTo, lineTo, cubicTo, close)
• Documented SvgPathStringSource parsing API
• Documented PathSegmentData segment representation
• Documented SvgPathNormalizer and helper functions
• Removed public_member_api_docs from lint ignores in ignore_for_file

Fixes: flutter/flutter#157939

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

No tests needed for doc-only changes (covered by test exemption).

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Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

[gemini-code-assist]

Code Review

This pull request adds documentation for all public API members in the path_parsing package and removes the corresponding lint suppression. Documentation was added to the PathProxy, SvgPathStringSource, PathSegmentData, and SvgPathNormalizer classes, as well as several utility functions. A review comment suggests generalizing the documentation for the PathSegmentData constructor to accurately reflect all initialized fields.

[stuartmorgan-g]

Marking as a draft per https://discord.com/channels/608014603317936148/1496222412767887483/1501225797057253527

Once this has passed review from a community member familiar with the Flutter review process, please mark it as ready for team review.