Support array, struct, and other complex introspection-backed params

[cgasgarth]

Goal

Extend agent coverage for the remaining high-value complex params that are still outside the generic descriptor model.

Current state

• This issue is partially outdated: array-backed and curve-style controls are no longer universally dropped.
• We already expose custom synthetic descriptors for rgblevels handles and colorzones bands, even though they depend on non-trivial underlying data structures.
• The generic widget-to-field path still only maps numeric scalar fields, enums, and bools.

Remaining gap

• There is still no reusable framework for array, struct, or other complex introspection-backed params.
• Current support is bespoke and module-specific rather than general.
• Many complex controls remain unreachable unless we add either targeted bindings or a broader abstraction layer.

Scope

• Inventory the highest-value remaining controls backed by ARRAY, STRUCT, and similar field types.
• Prefer reusable abstractions where they stay truthful to the underlying edit model.
• Use targeted synthetic bindings when a generic model would be unsafe, misleading, or too lossy.

Acceptance Criteria

• At least one additional high-value complex control family becomes agent-editable beyond the current rgblevels / colorzones support.
• The implementation makes clear which cases are handled generically versus by bespoke bindings.
• Protocol safety and deterministic execution are preserved for every newly exposed control.