Review public API before first beta

[Zhortein]

Objective

Review the public API before publishing the first beta.

Context

A beta release sends the signal that the main feature set is now mostly in place and should begin stabilizing.

Before tagging v0.3.0-beta.1, review the public API surface and identify risks.

Scope

Review public or semi-public APIs including:

• #[AsDatatable];
• DatatableInterface;
• DatatableDefinition;
• column definitions;
• filter definitions;
• advanced filter expression APIs;
• action definitions;
• bulk action definitions;
• join/custom join definitions;
• aggregate column definitions;
• export writer interfaces;
• preference provider interfaces;
• action visibility/security interfaces;
• Twig function API;
• runtime options passed to zhortein_datatable();
• Twig template override context;
• Stimulus data attributes that host apps may rely on.

Tasks

• Update docs/public-api-review.md.
• Mark APIs as stable-ish, experimental or internal.
• List API risks before 1.0.
• Identify any immediate API rename/deprecation needed before beta.
• Avoid code changes unless a small naming fix is clearly necessary and safe.

Acceptance criteria

• Public API review is updated.
• Experimental APIs are identified.
• Internal APIs are identified where possible.
• 1.0 API risks are documented.
• Any beta-blocking API issue is tracked.
• QA passes.