skill-formula-condition-abort-scope.md

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Docs-only: the objectstack-formula skill's previous binding-scope table never said what an unevaluable hook condition now costs (#4814).

§5 ("Update hook condition — previous vs record") is where an AI author is taught to write previous.x != record.x, and the mechanical translation table sends OLD.x / ISCHANGED(x) to the same place. The table listed exactly where previous is unbound — insert events, and multi: true predicate bulk updates — and then closed with "referencing previous where it is unbound makes the whole expression unevaluable", which was the pre-17 outcome: a logger.warn and a hook that did not fire.

#4775 changed that outcome: an unevaluable condition aborts the operation, before* and after* in the same direction, with an error naming the hook and the key. So the table's own rows changed meaning — "this quietly disables your hook" became "this fails your write" — without a word of the table changing. That is the drift this fixes: the surface teaching the idiom was the one surface still describing the old consequence.

Adds, in §5:

• the #4775 rule, with the reason the two outcomes had to split (a before* guard swallowed into false let writes through; an audit hook swallowed into false dropped records — opposite failures out of one collapsed result), and the note that onError is not an escape from it (it governs a handler that throws; the condition is evaluated before any handler runs);
• the multi: true cell in full (#4800/B1): one hook condition reading previous.* fails every predicate bulk update of that object, fail-loud takes no exception, and the error is a diagnosis — it names the batch, says the N matched rows have no single prior record, and gives the two real ways out (drop previous, or write by id). A record-change flow trigger is explicitly not one of them: it binds the same lifecycle hook and gets the same unbound previous. record is the bare payload on that path too, so a declared field this write does not set is unevaluable as well.

Plus a pointer under the legacy → CEL table, since OLD.x / ISCHANGED(x) are how a migrating author arrives at previous.x in the first place.

Releases nothing.