docs: document spec compliance and extensions vs jmespath.org

[Copilot]

This library is a strict superset of the JMESPath specification — all 25 standard functions pass the official compliance suite, but the library ships intentional extensions that diverge from the spec.

Changes

• New section: "Differences from the JMESPath specification" — exhaustive table-driven documentation of every deviation from the official spec:

  • Non-standard arithmetic functions: add, sub, mult, div, remove
  • $ root variable access (not in spec)
  • useCaseInsensitiveComparison option (not in spec)
  • Lenient null handling — where the spec would throw a type error, this library returns false/0
  • to_number extended to parse ISO 8601 date strings → Unix ms timestamp (spec returns null)
  • starts_with/ends_with with empty-string prefix/suffix returns false (spec is silent)

• Link to spec — "JMESPath" in the opening paragraph now links to https://jmespath.org/

Conventional Commit

docs(readme): document spec compliance and extensions vs jmespath.org

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• jmespath.org
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
  • Triggering command: /usr/bin/python3 python3 -c import urllib.request try: with urllib.request.urlopen('REDACTED', timeout=10) as r: print(r.read(5000).decode()) except Exception as e: print('Error:', e) (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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