#3600 local_source_failed drops the indexing error: a transient local extension failure leaves no cause (follow-up to 1672)

What happens

When a local source extension fails to index, swamp reports that the type couldn't be loaded, but not why:

{"event":"auto_resolve","status":"failed","type":"@test/gc-fixture","reason":"local_source_failed"}

In log mode it says "<type> could not be loaded — a local source extension failed to index" and suggests swamp doctor extensions. The bundler or loader error that made indexing fail is dropped. For a transient failure, which is when this usually happens, doctor extensions run afterwards finds nothing, so the cause is lost.

Lab 1672 introduced this message to replace a misleading collective_not_trusted. Its "Expected" section also asked for the underlying error ("file path + underlying bundler/loader error"), and that part didn't ship.

Seen in

swamp-uat's datastore suite, on stable, in two runs about two weeks apart. Each time, swamp model create @test/gc-fixture … in a fresh repo with the checked-in extensions/models/test/gc-fixture.ts failed with only:

"error": "Unknown model type: @test/gc-fixture. Available types: command/shell, @test/side-effect, @test/write-then-wait"
{"event":"auto_resolve","status":"failed","type":"@test/gc-fixture","reason":"local_source_failed"}

• https://github.com/swamp-club/swamp-uat/actions/runs/38629484717 (data delete row, [git-config] [filesystem], 2026-10-14)
• the data prune row in the same configuration, 2026-10-13 nightly

The other local fixtures in the same repo (@test/side-effect, @test/write-then-wait) loaded. It didn't reproduce in 40 local runs of those rows under parallel load. The fixture and test are unchanged between passing and failing runs, so the failure is transient, and without the error there's nothing to go on.

Where it's dropped

ExtensionAutoResolver.resolve (src/domain/extensions/extension_auto_resolver.ts, around line 327) calls extensionInstaller.failedLocalSourceMatchesType(type), which returns only a boolean. output.localSourceFailed(type) → renderAutoResolveLocalSourceFailed(type, mode) then has nothing to report. The installer recorded the failed source, so the error is available at that point.

Expected

• The local_source_failed event carries the failing source file and the indexing error, for example "file": "extensions/models/test/gc-fixture.ts", "error": "<bundler/loader message>". The log-mode message prints both.
• The suggestion to run swamp doctor extensions can stay, but the message shouldn't depend on it for a transient failure.