The coverage IT runs an attachment upload and a snapshot mint

[nedelcho-delchev-tues]

Fixes #7623

#7568 put a drop of every system-owned column at the top of the generated repository's save(). IntentEmissionCoverageIT was green on that PR, and the change still broke every function: Attachment upload and every function: Snapshot mint — the fixture declared neither. Its own readOnly columns are all written through updateProperties by the generated jobs, notifications and task write-backs, which never reach save(), so a regression on the create path of a system writer was invisible to the one IT that is supposed to compile and run the whole generated surface.

The fixture gains both families. An Archive document master with an items child, an ArchiveFile (function: Attachment) and an ArchiveCopy (function: Snapshot), plus a process that runs the generated snapshot delegate twice in one run so the copy's Version goes 1 then 2 while the document's own identity does not move.

The assertions go through HTTP against the generated controllers, because reading the rendered template proved nothing about the row the last time:

1. the upload answers with the five metadata columns, and the stored row carries them — read back through the master-scoped list and then by id, with StoragePath ending in the Uuid folder of the stored file, so the two columns name one object rather than merely both being present;
2. the file downloads byte for byte through the generated endpoint;
3. a plain POST carrying all five still stores null for each of them while keeping the authored Caption (intent: readOnly and system-owned columns are preserved on update only - a POST stores any value for them #7549 stays fixed);
4. the document carries two copies, Version 1 and 2, each with a non-null file name, application/pdf, a non-zero size and a /Attachments/ArchiveCopy/ path.

The entities constant was already at the 65535-byte limit for a Java string constant, so the two families ride in a third constant concatenated between the entities and the glue — one document, three constants, for the same reason the glue was split out.

components/engine/engine-intent/CLAUDE.md now names the seven writer families whose create path is save() (REST create, attachment upload, snapshot mint, create-from, postings:/posts:, inbound: arrivals, aggregates: first row), so a change to Repository.java.template's save() or update() is checked against each one by name rather than against "the coverage IT is green".

Verified locally: IntentEmissionCoverageIT passes, 173 s.