feat(core): compose effect collections

Support Vec<T: IntoEffect> and [T; N] batches so dynamic reusable partial updates compose inside the existing effect model without a broad IntoIterator blanket impl.

req: canonical_authoring/003

REQUIREMENTS.md

@@ -53,7 +53,7 @@ client app state framework.
 002	Typed partial swaps are the primary UX, not an advanced feature: handlers change domain state in Rust, convert domain values into view values, render hemplate partials through generated helpers, and place them into generated targets. The real primitive is generated target + rendered partial + swap kind. [north_star]
 
 ### req: canonical/003
-003	Canonical keyed-row CRUD reads like ordinary Rust intent: create appends a rendered row partial, update/toggle replaces a keyed row partial, delete removes a keyed row, summary/text/form effects compose in tuples or arrays implementing `IntoEffect`, and no handler chooses a target with a CSS selector. [north_star]
+003	Canonical keyed-row CRUD reads like ordinary Rust intent: create appends a rendered row partial, update/toggle replaces a keyed row partial, delete removes a keyed row, summary/text/form effects compose in tuples, arrays, or `Vec<T: IntoEffect>` for dynamic batches, and no handler chooses a target with a CSS selector. [north_star]
 
 ### req: canonical/004
 004	Generated helpers may compose only facts uniquely known from templates and checked Rust types: template, slot, optional key, form/control, class token, explicit island/event marker, and effect kind. If a handler parameter, key, form, target, raw route, or legacy target would require guessing, the user must say it explicitly and diagnostics must point to the Rust and hemplate spans. [north_star]