The two-registry gap, surfaced as data and linted only on request (ADR-0004 decision 8).

A block type whose emitted invoke type has no handler registered under st-ADR-0051 fails at runtime with error.execution, not at authoring time. That gap is real, and this module is the whole of what the compiler does about it.

Always published, because it is a fact about the compile

collect/1 returns every <invoke type="..."> in the generated chart with the block that emitted it, and StatifierBlocks.Compiled's invoke_types is the sorted set of those strings. That part is unconditionally right and needs no opt-in: the host compares it against its own registration at deploy time, when it knows both, and this field is what makes that a one-liner.

A typeexpr is deliberately not collected. It names a type computed at run time out of the datamodel, so there is no string here to compare against a registration, and reporting the expression source as though it were a type would be worse than reporting nothing.

Linted only on request, and only ever a warning

lint/3 runs when the caller passes :known_invoke_types, and it emits a warning naming the block and the type for each emitted type absent from the set. Never an error, and the reason is a lifetime mismatch rather than timidity:

st-ADR-0051 made the handler set deployment state, supplied per session and fixed for the session's lifetime. The palette is authoring state, supplied per operation. An authoring server that never runs a chart has no handler map at all, and if a missing handler failed the compile that host could not compile - this package would have made a runtime concern a precondition of authoring. Worse, it would be wrong even where a set is available: a host may compile in an authoring service and run in a worker with a different registration, so any set handed to the compiler is one deployment's belief, not ground truth. A warning is the strongest claim the evidence supports.

The set a host passes is exactly Map.keys(invoke_handlers) from its Statifier.Session options - the same map st-ADR-0051 turns into Statifier.Invoke.Types - so the comparison is over the same strings the runtime classifier will use.