docs: split README into quick-start + reference pages under docs/

Trim README.md to a quick-start guide (install, init, generate, sync,
clean) with a main-flags table and feature-toggle summary, and move the
detailed reference material into focused pages under docs/:
installation, usage, configuration, generation, publishing, templates.

Correctness fixes carried over during the split:
- The 'Site generated ... with <URL>' source link lives in the page
  header bar (header.tmpl), not the footer (footer.tmpl only renders
  the tarball download). Fixed in docs and the SOURCE_URL code comment.
- --sync is a config-backed action and accepts --config PATH / reads
  ./shuriken.conf; the --config action list now includes it.
- --refresh-splash also re-copies the site favicon; documented.
- State the Bash 5.1 requirement (enforced by the script) in the docs.
- docs/stats-exif-audit.md: the EXIF cache moved to
  metadata-cache.source.sh and the native-field parser extension was
  implemented; add a status note and fix the stale module path.

bin/shuriken regenerated from the config.source.sh comment change.

1 files changed, 34 insertions, 0 deletions

diff --git a/docs/templates.md b/docs/templates.md
new file mode 100644
index 0000000..f34be9d
--- /dev/null
+++ b/docs/templates.md
@@ -0,0 +1,34 @@
+# HTML templates
+
+Templates live under `share/templates/default` in the source tree and under the
+installed template directory (`/usr/share/shuriken/templates/default`) after
+installation.
+
+The stock default resolves to the installed template directory when it exists,
+and otherwise falls back to the source tree's `share/templates/default` when
+running from a checkout. Copy and edit templates, then point `TEMPLATE_DIR` or
+`--template PATH` at the customized directory.
+
+## Required templates
+
+A template directory must contain these `.tmpl` files (validated before
+generation):
+
+`details`, `footer`, `header`, `next`, `prev`, `preview`, `previewpage`,
+`redirect`, `view`.
+
+When `SPLASH_PAGE=yes`, the `splash` template is also required.
+
+## Stats templates
+
+The stats site adds two more templates, `camera.tmpl` and `cameraview.tmpl`
+(per-camera mini-album), plus `stats.tmpl` for the overview page. These are only
+used when `STATS_PAGE=yes`.
+
+## Header bar and footer
+
+* The page **header bar** (`header.tmpl`) renders the "Site generated … with
+  <SOURCE_URL>" link and, when `STATS_PAGE=yes`, the `Stats` navigation
+  link.
+* The page **footer** (`footer.tmpl`) renders the "Download all photos in
+  original size" tarball link, shown only when `TARBALL_INCLUDE=yes`.
\ No newline at end of file