Notes: Restore note-ID metadata helpers on the suggest-mode stack

The suggest-mode stack diverged from trunk before #75147 landed, so
addNoteIdToMetadata and getNoteIdsFromMetadata are absent from this
branch's collab-sidebar/utils.js. suggestion-mode/provider.js imports
both, breaking the JS bundle build (esbuild: no matching export) and
cascading into the PHP, Playwright, and release checks.

Vendor the two pure helpers verbatim from trunk (786c69c) so this
PR builds independently of a full-stack rebase. They resolve cleanly
against trunk's identical definitions when the stack is updated.

Author: adamsilverstein

packages/editor/src/components/collab-sidebar/utils.js

@@ -275,3 +275,42 @@ export function scrollNoteThreadIntoView( noteId, container ) {
 		element?.scrollIntoView( { block: 'nearest' } );
 	} );
 }
+
+/**
+ * Reads the note IDs from block metadata as a normalized array,
+ * preserving insertion order. Handles both scalar (legacy, possibly
+ * string-typed) and array (new) values.
+ *
+ * @param {Object} metadata Block metadata object
+ * @return {number[]} Array of note IDs (may be empty)
+ */
+export function getNoteIdsFromMetadata( metadata ) {
+	const noteId = metadata?.noteId;
+	const raw = Array.isArray( noteId ) ? noteId : [ noteId ];
+	const ids = new Set();
+	for ( const value of raw ) {
+		const id = Number( value );
+		if ( Number.isFinite( id ) && id > 0 ) {
+			ids.add( id );
+		}
+	}
+	return [ ...ids ];
+}
+
+/**
+ * Adds a note ID to the metadata.
+ * Converts scalar to array if needed, otherwise appends.
+ *
+ * @param {Object} metadata Existing block metadata
+ * @param {number} noteId   Note ID to add
+ * @return {Object} Updated metadata object
+ */
+export function addNoteIdToMetadata( metadata, noteId ) {
+	const ids = new Set( getNoteIdsFromMetadata( metadata ) );
+	const id = Number( noteId );
+	if ( ids.has( id ) ) {
+		return metadata;
+	}
+	ids.add( id );
+	return { ...metadata, noteId: [ ...ids ] };
+}