docs: add arc output connector for cloud (#557)

* docs: add arc output connector for cloud

Add arc output connector page and update whats-new with entry for the
new cloud-supported connector.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* chore: temporarily reference auto-docs branch from rp-connect-docs

Update playbook to reference the auto-docs/update-rpcn-connector-docs
branch so the arc connector include can resolve during preview builds.

This should be reverted to main once the rp-connect-docs PR is merged.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* Update local-antora-playbook.yml

* Update nav.adoc

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: 2 people

modules/ROOT/nav.adoc

@@ -171,6 +171,7 @@
 
 *** xref:develop:connect/components/outputs/about.adoc[]
 **** xref:develop:connect/components/outputs/amqp_0_9.adoc[]
+**** xref:develop:connect/components/outputs/arc.adoc[]
 **** xref:develop:connect/components/outputs/aws_dynamodb.adoc[]
 **** xref:develop:connect/components/outputs/aws_kinesis.adoc[]
 **** xref:develop:connect/components/outputs/aws_kinesis_firehose.adoc[]

modules/develop/pages/connect/components/outputs/arc.adoc

@@ -0,0 +1,3 @@
+= arc
+:page-aliases: components:outputs/arc.adoc
+include::redpanda-connect:components:outputs/arc.adoc[tag=single-source]

modules/get-started/pages/whats-new-cloud.adoc

@@ -22,6 +22,8 @@ Serverless clusters now support up to 100 Redpanda Connect pipelines and 100 MCP
 === Redpanda Connect updates
 
 * The Redpanda Connect pipeline creation and editing workflow has been simplified. The new UI replaces the previous multi-page wizard with a visual pipeline diagram, an IDE-like configuration editor, slash commands for inserting variables, and inline links to component documentation. See the xref:develop:connect/connect-quickstart.adoc[Redpanda Connect quickstart] to try it out.
+* Outputs:
+** xref:develop:connect/components/outputs/arc.adoc[arc]: Send data to an Arc columnar analytical database using its high-performance MessagePack ingestion endpoint.
 * Processors:
 ** xref:develop:connect/components/processors/string_split.adoc[string_split]: Splits strings into multiple parts using a delimiter, creating new messages or fields for each part.