fix(classification): address code review feedback on path classification performance and consistency

[Copilot]

Addresses four issues identified in code review of path classification implementation:

Changes

• Performance: Replace to_ascii_lowercase() allocations in registry path matching with zero-copy eq_ignore_ascii_case() byte slice comparison. Eliminates repeated string allocations for static pattern matching.

• Duplicate tag prevention: Consolidate three separate path classification checks into single conditional to prevent multiple Tag::FilePath entries. Implementation now matches documented behavior.

• Documentation clarity: Clarify Windows path validation rules to distinguish consecutive backslashes (folder\\\\file.txt is invalid) from UNC prefix (\\\\server\\share is valid).

• Test documentation: Add rationale comment for 500ms performance test timeout explaining CI runner variance tolerance.

Code Impact

Before (inefficient):

pub fn is_suspicious_registry_path(&self, text: &str) -> bool {
    let text_lower = text.to_ascii_lowercase();
    SUSPICIOUS_REGISTRY_PATHS
        .iter()
        .any(|path| text_lower.contains(&path.to_ascii_lowercase()))
}

After (zero-allocation):

pub fn is_suspicious_registry_path(&self, text: &str) -> bool {
    SUSPICIOUS_REGISTRY_PATHS
        .iter()
        .any(|path| self.contains_ascii_case_insensitive(text, path))
}

fn contains_ascii_case_insensitive(&self, haystack: &str, needle: &str) -> bool {
    haystack.as_bytes()
        .windows(needle.len())
        .any(|window| window.eq_ignore_ascii_case(needle.as_bytes()))
}

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[coderabbitai]

Important

Review skipped

Bot user detected.

To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}