docs(intent): the assistant guide documents the notify fan-out (forEach)

[delchev]

The notify fan-out shipped with #6435 — NotificationIntent.forEach, NotifySupport.fanOut, the forEach* glue keys, Send.java.template's per-row loop and thirteen GlueSendDocumentTest cases are all on master — but the authoring guide never got its section.

On master, intent-assistant-guide.md has no mention of it: no "fan-out", no "one message per related row", and the keyword table lists notify attach while omitting notify forEach. The only forEach the guide describes is the unrelated generates/children collection (forEach: { entity: … } / forEach: { days: … }).

That matters more than a normal doc gap: this guide is the resource fed to the Intent Editor's AI assistant, so the assistant cannot author a keyword the engine already accepts — and would plausibly reach for the generates-style map shape, which a notify block does not take.

The text was written when the feature was built and never left a working tree.

What it documents

• the shape — forEach: <Entity>, after which every path resolves against the row: the recipient, the {placeholders}, and attach: print (the row's own document);
• the exactly-one-to-one-back-relation rule, and that zero and ambiguous are both validation errors;
• why a fan-out is fail-soft per row rather than failing the step: a retry would re-mail everyone already served, so a partial send cannot be made idempotent;
• one keyword-table row.

Verified against master, not trusted

Every claim was checked before writing it down:

Claim	Where it holds
forEach: <Entity> is a plain string	NotificationIntent.forEach
zero / ambiguous back-reference are validation errors	IntentParser.validateNotifyBlock — unknown entity, and backReferencesTo(...) != 1
skip no-recipient, log a failure, complete with a summary	Send.java.template — sent / skipped / failed counters + summary log
attach: print renders the row's document	validateNotifyBlock re-points aboutEntity at the row entity

Docs only — no code, no behaviour change.

🤖 Generated with Claude Code