[CorieW]

Fixes #3292. Sets the extension's runtime settings on processQueue, as #3234 and #3276 did for the other kits. Rebased from the closed #3233.

	Extension	Kit before	Kit after
Concurrency	1	80	1
CPU	0.1666	1	0.1666 (gcf_gen1)
Ingress	ALLOW_INTERNAL_ONLY	ALLOW_ALL	ALLOW_INTERNAL_ONLY

At concurrency 80, a burst of mail with attachments ran one 256MiB instance out of memory. Every event on it was dropped and never retried, so the mail was never sent.

Testing

• npm test passes (174 tests).
• Live results are in fix(firestore-send-email): kit/extension parity – bursts of mail with attachments run the kit out of memory and the mail is never sent #3292: with the same change, all 20 large-attachment emails were sent. Before, 12–17 were not. Not re-run live from this branch.

[gemini-code-assist]

Code Review

This pull request configures the processQueue Cloud Function in the firestore-send-email kit to deploy with specific runtime settings: concurrency: 1, cpu: "gcf_gen1", and ingressSettings: "ALLOW_INTERNAL_ONLY". This prevents out-of-memory errors and dropped events when handling bursts of emails with attachments on 256MiB instances. Documentation, changelog, and tests have been updated accordingly. I have no feedback to provide.