Share clipEmbedding, and shorten the README's keyword sentences

clipKeywords takes the CLIP embedding out of a file's ML data with
clipEmbedding, now exported from src/library/mldata.ts, and adds only its own
checks: 512 numbers, not all zero. bin/clip-keyword-vectors puts its body in
a main function called at the bottom, as the scripts under script/ do; it
writes the same files. The README lists the Discover categories as bullets
and states the score, the rule and the video rule in short sentences of their
own.

Model: opus-5-5

bin/clip-keyword-vectors

@@ -5,21 +5,26 @@
 # no gate runs it. It downloads about 215 MB, most of it Ente's two CLIP models.
 set -eu
 
-cd "$(dirname "$0")/.."
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 # python:3.13-slim (Python 3.13.17 on Debian 13.7), 2026-10-21. The wheels
 # below are the ones for this image on linux/amd64.
-image=python@sha256:57b29a7c050c4e679e4bea572e14b3965cf4b5839de2da49d55e49ffc4024f39
+IMAGE=python@sha256:57b29a7c050c4e679e4bea572e14b3965cf4b5839de2da49d55e49ffc4024f39
 
-docker run --rm -i --platform linux/amd64 \
-    --user "$(id -u):$(id -g)" -e HOME=/tmp \
-    -v "$PWD:/repo" -w /repo "$image" sh -c '
-        python -m venv /tmp/venv &&
-        /tmp/venv/bin/pip install --quiet --disable-pip-version-check \
-            --no-cache-dir --no-deps --require-hashes -r /dev/stdin &&
-        /tmp/venv/bin/python bin/clip-keyword-vectors.py' <<'EOF'
+main() {
+    cd "$ROOT"
+    docker run --rm -i --platform linux/amd64 \
+        --user "$(id -u):$(id -g)" -e HOME=/tmp \
+        -v "$ROOT:/repo" -w /repo "$IMAGE" sh -c '
+            python -m venv /tmp/venv &&
+            /tmp/venv/bin/pip install --quiet --disable-pip-version-check \
+                --no-cache-dir --no-deps --require-hashes -r /dev/stdin &&
+            /tmp/venv/bin/python bin/clip-keyword-vectors.py' <<'EOF'
 numpy==2.5.3 --hash=sha256:a5fa86b80fd24bcd1aff83ad23be44ea323de3f787be8f8b15d4a65621e25321
 onnxruntime==1.30.0 --hash=sha256:86f940afc801ea9681a4da8af84fbe95e1d9ea7d80903952cc1bfad54faad38f
 pillow==12.3.0 --hash=sha256:0847a763afefb695bc912d7c131e7e0632d4edc1d8698f58ddabec8e46b8b6d3
 tokenizers==0.23.2 --hash=sha256:41c2f84d172449b4dadb9cdc508e3e364076613c35b16e76ecfe47a60d1e3305
 EOF
+}
+
+main "$@"