Build stamp, live listening strip, OG cards, closer shiki ground

- footer: 'built <ts> · <hash> · <n> notes', hash linking to Gitea
  (GARDEN_COMMIT passed in by build.sh; '+' marks dirty-tree builds)
- homepage header: live strip fed by api.c0smere.net/spotify/summary
  (weekly aggregate + monthly top artist/genre), fail-closed like the
  odometer and header quote
- /og/<slug>.png satori+resvg cards for every note + the homepage;
  og:/twitter: meta in Base
- shiki github-dark-default (#0d1117 sits closer to the page ground)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

deploy/build.sh

@@ -5,6 +5,13 @@ set -eu
 
 VAULT="${VAULT:-/home/nox/docker/obsidian/vaults/weeslahw_coppermind}"
 
+# footer build stamp: the node container has no git, so resolve the
+# commit here ("+" = dirty tree, e.g. a local-state build after a failed pull)
+COMMIT=$(git rev-parse --short HEAD 2>/dev/null || echo '')
+if [ -n "$COMMIT" ] && ! git diff --quiet 2>/dev/null; then
+    COMMIT="${COMMIT}+"
+fi
+
 # --user: build artifacts (node_modules, dist, public/assets) must stay
 # owned by the invoking user, or the next git pull can't write the tree
 docker run --rm \
@@ -12,6 +19,7 @@ docker run --rm \
     -v "$(pwd):/app" \
     -v "$VAULT:/content:ro" \
     -e GARDEN_CONTENT=/content/Digital_Garden \
+    -e GARDEN_COMMIT="$COMMIT" \
     -e ASTRO_TELEMETRY_DISABLED=1 \
     -e HOME=/tmp \
     -e npm_config_cache=/tmp/.npm \