spine: a .ocda.db can be fetched, as a pod zip can

A URL ending in .ocda.db is now downloaded and processed in place,
through the path that already did it for .zip: the same curl call, the
same size and timeout limits, the same refusal of local and private
addresses, the same --allow-downloads guard, the same temp file cleanup.
Only the pattern had to widen.

  rgx_url_zip     ^https?://...[.]zip$
  rgx_url_source  ^https?://...([.]zip|[.]ocda[.]db)$

downloadZipUrl is no downloadSourceUrl and the download temp directory
is spine-download rather than spine-zip-pod; (the extraction directory
keeps its name, being still only for zips).

(assisted by Claude-Code)

1 files changed, 13 insertions, 21 deletions

diff --git a/src/sisudoc/ocda/abstraction/load.d b/src/sisudoc/ocda/abstraction/load.d
index ebdd1a5..ea387d1 100644
--- a/src/sisudoc/ocda/abstraction/load.d
+++ b/src/sisudoc/ocda/abstraction/load.d
@@ -50,38 +50,30 @@
 module sisudoc.ocda.abstraction.load;
 @safe:
 /+ ↓ one way in, whatever the document is being read from
-
      spine's pipeline is markup -> abstraction -> output. once the abstraction
      is serialised, there is more than one thing an abstraction can be read
      from, and a consumer should not have to know which it was handed:
-
+     .
        .sst / .ssm  + images   the markup source
        pod (dir)    + images   the same, bundled
        pod .zip                the same, zipped
        .ssp         + images   the abstraction, as text
        .ocda.db                the abstraction, sqlite, images inside
-
-     A source may also be remote. spine already takes a URL argument ending
-     in .zip: it is downloaded to a temp file (downloadZipUrl in
-     ocda/io_in/read_zip_pod.d, guarded by rgx_url_zip and by --allow-
-     downloads) and the local path is processed in its place. The same should
-     be offered for .ocda.db, which is the one other artefact that is
-     self-sufficient enough to be fetched on its own: it carries its images.
-     What that needs is small and is not done here:
-
-       - rgx_url_zip is `^https?://...[.]zip$`; a sibling pattern for
-         `[.]ocda[.]db$`, or one pattern covering both
-       - the same download path, which is already generic apart from that
-         regex, and the same temp-file cleanup
-       - dispatch, which this module already does once the file is local
-
-     A .ssp URL would want its images too, so it is a pod or a database that
-     travels, not a .ssp on its own.
-
+     .
+     A source may also be remote. A URL ending in .zip or in .ocda.db is
+     downloaded to a temp file (downloadSourceUrl in
+     ocda/io_in/read_zip_pod.d, guarded by rgx_url_source and by
+     --allow-downloads) and the local path is processed in its place.
+
+     Those two travel because each is self-sufficient: a pod holds its
+     source and images, a .ocda.db holds its abstraction and images. A .ssp
+     does not, describing its images by name and digest without carrying
+     them, so it would arrive without them and is not fetched.
+     .
      This module names those sources, tells them apart, and loads the two
      that are self-describing artefacts, returning the value the parser
      produces.
-
+     .
      The three source forms are deliberately *not* loaded here. They are the
      parser's job (sisudoc.ocda.meta.metadoc, spineAbstraction), and it needs
      the environment, the options and the configuration that spine.d