Avoid mass noun lints for ing modifiers

[puneetdixit200]

Issues

Fixes #1994

Description

This updates the mass noun countability rule to avoid treating -ing words as countability errors when they are acting as present-participle modifiers before a noun head.

It covers adjective chains such as a working direct link and slash-separated modifier chains such as a prototyping/testing/learning tool, while preserving existing mass-noun corrections like one clothing based on weather conditions.

Demo

N/A; linter behavior is covered by unit tests.

How Has This Been Tested?

• CARGO_HOME=$PWD/.cargo-home CARGO_TARGET_DIR=$PWD/target cargo test -p harper-core linting::mass_nouns::noun_countability::tests:: -- --nocapture
• CARGO_HOME=$PWD/.cargo-home CARGO_TARGET_DIR=$PWD/target cargo fmt --check
• CARGO_HOME=$PWD/.cargo-home CARGO_TARGET_DIR=$PWD/target cargo test -p harper-core
• git diff --check

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

OpenAI GPT-5 assisted with the implementation and validation.

If Your PR Implements or Enhances a Linter

• I made up the sentences in the unit tests.
• The sentences in the unit tests were generated by an AI.
• I'm using examples from the bug report / feature request.
• I collected real-world sentences for the unit tests.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.