Split album-metadata.source.sh into focused modules (6r0)

album-metadata.source.sh aggregated six unrelated concerns. Move each
along its existing seam (pure mechanical move, no logic changes):

- EXIF presentation (photo_exif_details_html, tooltip helpers, the
  _photo_exif_values_to wrapper) stays in album-metadata.source.sh,
  which is now EXIF-presentation only.
- File counting (count_files, count_incoming_images, count_tree_files)
  -> image.source.sh, which already owns incoming_image_files;
  count_incoming_images is a direct wrapper of it.
- Tarball naming (tarball_name_plan, generated_tarball_name) ->
  archive.source.sh, which already owns tarball()/resolve_tar_opts.
- Generation metadata + JSON (_collect_generation_metadata,
  _generation_metadata_json, write_generation_metadata) -> new
  generation-metadata.source.sh.
- Dry-run (dry_run, collect_dry_run_*, print_dry_run_plan) -> new
  dry-run.source.sh.
- clear_exif_cache -> metadata-cache.source.sh, next to the cache
  primitive cached_photo_identify_output.

LIB_SOURCES (Justfile + src/shuriken.sh): insert generation-metadata
and dry-run right after album-metadata, before album-render/album.
They depend on image, archive, template and metadata-cache (all earlier
or runtime-only calls), and are consumed by the album coordinator and
the dry-run CLI action, which come later. bin/shuriken regenerated via
just build. File-header comments updated to reflect the new homes.

just test, just shellcheck, just check-generated and git diff --check
all pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/src/lib/image.source.sh b/src/lib/image.source.sh
index f7cb715..2581228 100644
--- a/src/lib/image.source.sh
+++ b/src/lib/image.source.sh
@@ -53,6 +53,44 @@ incoming_image_files() {
         | sort
 }
 
+# File counters for the source tree and the generated dist. Moved here from
+# album-metadata.source.sh (task 6r0): counting incoming/generated files is part
+# of this module's file-enumeration concern -- count_incoming_images is a direct
+# wrapper of incoming_image_files above, and count_files/count_tree_files are the
+# generic siblings the generation-metadata and dry-run modules use to tally the
+# produced photos, thumbs and HTML pages. Behaviour and signatures are unchanged.
+count_files() {
+    local -r dir="$1"; shift
+    local -r name="${1:-}"; shift || true
+
+    if [ ! -d "$dir" ]; then
+        printf '0\n'
+        return
+    fi
+
+    if [ -n "$name" ]; then
+        find "$dir" -maxdepth 1 -type f -name "$name" | wc -l
+    else
+        find "$dir" -maxdepth 1 -type f | wc -l
+    fi
+}
+
+count_incoming_images() {
+    incoming_image_files | wc -l
+}
+
+count_tree_files() {
+    local -r dir="$1"; shift
+    local -r name="$1"; shift
+
+    if [ ! -d "$dir" ]; then
+        printf '0\n'
+        return
+    fi
+
+    find "$dir" -type f -name "$name" | wc -l
+}
+
 warn_unsupported_incoming_files() {
     local file