feat: support all 16 IANA-registered Cache-Control directives

[tusbar]

Add must-understand directive (RFC 9111 §5.2.2.3), qualified forms for no-cache and private with field-name lists (RFC 9111 §5.2.2.4, §5.2.2.7), and edge case tests for malformed headers.

• Add mustUnderstand boolean property
• Add noCacheFields and privateFields string array properties
• Fix no-cache="Set-Cookie" incorrectly parsed as noCache: false
• Fix private="Set-Cookie" incorrectly parsed as private: false
• Refactor parser to use matchAll for proper quoted-value extraction
• Extract format helpers to reduce complexity
• Add robustness tests (unclosed quotes, negative/huge durations, etc.)
• Update README with full directive tables and RFC references
• Update keywords to reference RFC 9111, RFC 8246, RFC 5861
• Validate field names against RFC 9110 token grammar when formatting
• Add JSDoc documentation to exported symbols

BREAKING CHANGE: noCache and private now correctly return true when the directive is present with field-name arguments (e.g. no-cache="Set-Cookie"). Previously these were incorrectly parsed as false, silently dropping the directive.

Closes #2
Closes #3

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e9d594e) to head (b938fe1).
⚠️ Report is 4 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            1         1           
  Lines           99       114   +15     
  Branches        23        17    -6     
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+ Hits            99       114   +15     

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[Copilot]

Pull request overview

This PR extends the Cache-Control parser/formatter to cover additional RFC 9111 directives and qualified forms, aligning behavior with IANA-registered directives and fixing previously incorrect parsing for no-cache/private when field-name arguments are present.

Changes:

• Add support for must-understand plus qualified no-cache / private field-name lists (noCacheFields, privateFields).
• Refactor parsing to use matchAll and refactor formatting via helper functions.
• Expand test coverage for edge cases and update README/package keywords with RFC references.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
src/index.ts	Adds new directive fields, updates parsing logic for qualified directives, and refactors formatting helpers.
__tests__/index.spec.ts	Adds tests for new directives, qualified field-name handling, and robustness edge cases.
README.md	Documents supported directives, qualified directives, and updates usage examples/RFC references.
package.json	Adds RFC-related keywords for discoverability.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

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[tusbar]

🎉 This PR is included in version 3.0.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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