rm0 wire stats feature into generate with STATS_PAGE toggle

Final integration of the stats-site feature:

- Add STATS_PAGE config (default yes) mirroring SPLASH_PAGE through every
  layer: shuriken.default.conf, apply_config_defaults, CLI_OPTION_SPEC
  (--stats/--no-stats), the CLI_CONFIG_OVERRIDE_TARGETS allowlist (without
  which the flag was silently ignored), usage text, yes/no validation,
  print_config, the action config list + effective-setting log, the
  generation metadata, and the dry-run plan.
- generate() now calls a gated generate_stats_pages helper after the album
  pages (and before archiving, so the stats/camera pages are tarballed):
  collect_photo_exif_stats + render_stats_page . . + render_camera_pages . .
- Emit "stats_page" in shuriken.json next to "splash_page".
- Gate the header Stats nav link behind STATS_PAGE via a new
  render_stats_page_html config_html field, so it is hidden (no 404) when
  stats are disabled.
- Document STATS_PAGE and --stats/--no-stats in the README.
- Tests: full --generate produces stats.html + camera-<slug>.html + the nav
  link and stats_page=true; --no-stats suppresses all three and sets
  stats_page=false; print-config and metadata expectations updated.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/src/lib/template.source.sh b/src/lib/template.source.sh
index 9fd3ad4..8e5b93e 100644
--- a/src/lib/template.source.sh
+++ b/src/lib/template.source.sh
@@ -167,6 +167,7 @@ declare -ra TEMPLATE_RENDER_FIELD_SPECS=(
     'render_redirect_page_html|context_html|redirect_page|redirect_page|redirect'
     'render_show_header_bar|context_raw|show_header_bar|show_header_bar|header'
     'render_stats_body_html|context_raw|stats_body|stats_body|stats'
+    'render_stats_page_html|config_html|STATS_PAGE||'
     'render_tarball_include|tarball_include|||'
     'render_tarball_name_html|context_html|tarball_name|tarball_name|footer'
     'render_thumbheight_html|config_html|THUMBHEIGHT||'
@@ -478,6 +479,12 @@ prepare_template_render_vars() {
                     ORIGINAL_BASEPATH)
                         context_value="$ORIGINAL_BASEPATH"
                         ;;
+                    STATS_PAGE)
+                        # Always defaulted by apply_config_defaults; degrade to
+                        # "no" (link hidden) if somehow unset so the header bar
+                        # never references a stats page that was not generated.
+                        context_value="${STATS_PAGE:-no}"
+                        ;;
                     THUMBHEIGHT)
                         # Refresh-only configs do not require generation
                         # sizing fields; render absent values as empty.