Enhance documentation and refactor agent handling and interfaces

[ericges]

Docs & agents update, list-view cleanup, AsFilterInvoker deprecation

Summary

Documentation-focused PR with a few small API cleanups. Adds comprehensive AI-agent guidance via AGENTS.md (with CLAUDE.md as a symlink), refactors the list-only Twig template to use the engine's view API, deprecates #[AsFilterInvoker], and removes unused methods from ModInterface and QueryHelperTrait.

Changes

Documentation

• AGENTS.md — substantially expanded guidance for AI coding agents:
  • Corrected the architecture flow diagram (adds ListSpecification, Loader, Mods; clarifies that Contexts and Projectors/Views are separate axes and that the Export context/projector/view are not yet implemented)
  • New "Notable subsystems" section (src/Specification/, src/Filter*/, src/Form/, src/Reader/, src/InferPtable/, src/Integration/, src/EventListener/NamedDispatch/)
  • Documented #[AsListCallback] and the @internal AsFlareCallback base attribute
  • Complete registry list (FilterCollectorRegistry, FlareCallbackRegistry, EngineModRegistry added)
  • New "Testing & CI" section: explicitly states there is no test suite yet and lists all CI workflows
  • Tooling additions (make phpstan-pro, make semgrep-sec; note that Mago runs in CI only) and updated PHPStan excludes
  • Updated Symfony version range to include ^7.0
• CLAUDE.md — added as a symlink to AGENTS.md so Claude Code picks up the same instructions (edit AGENTS.md only)

List handling / templates

• list_only.html.twig — now creates the view explicitly via {% set flare_list = flare.createView %} and iterates flare_list.entries instead of flare.entries

Deprecations & API cleanup

• #[AsFilterInvoker] — deprecated; filter invocation should be defined via the filter element's __invoke method instead. Removal planned for v0.2.
• Engine::addMod() — $config parameter now defaults to []
• ModInterface — removed the unused configureOptions(OptionsResolver $resolver) method (and the OptionsResolver dependency from the interface)
• QueryHelperTrait — removed the unused column() helper

Breaking changes

• Removing ModInterface::configureOptions() breaks custom engine mods that implement it (mods should drop the method).
• Templates relying on flare.entries in list_only.html.twig follow a new pattern; custom templates are unaffected but should adopt flare.createView going forward.

Notes

• No test suite exists yet; verified via PHPStan/CI workflows.