Rename script/install to script/fetch-policy

By convention, and in scripts-to-rule-them-all, script/install installs
the program itself. This script fetches the shared policy files into a
repo. The make target, the test names and the messages take the new
name. Behaviour is unchanged.

Model: opus-5-5

script/update-policy

@@ -1,12 +1,12 @@
 #!/bin/sh
 # script/update-policy: bring this repo up to standards. It fetches the
-# current script/install from the prompts repo over HTTP, runs it on this
-# repo and commits the files it wrote. It does not push. Identical in all
-# repos. Our own extension to scripts-to-rule-them-all.
+# current script/fetch-policy from the prompts repo over HTTP, runs it
+# on this repo and commits the files it wrote. It does not push.
+# Identical in all repos. Our own extension to scripts-to-rule-them-all.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-INSTALL_URL="https://git.eeqj.de/sneak/prompts/raw/branch/main/script/install"
+FETCH_POLICY_URL="https://git.eeqj.de/sneak/prompts/raw/branch/main/script/fetch-policy"
 
 die() {
     echo "update-policy: $*" >&2
@@ -22,10 +22,10 @@ main() {
     trap 'rm -rf "$tmp"' EXIT
 
     curl --fail --silent --show-error --max-time 60 \
-        --output "$tmp/install" "$INSTALL_URL" ||
-        die "cannot fetch $INSTALL_URL"
+        --output "$tmp/fetch-policy" "$FETCH_POLICY_URL" ||
+        die "cannot fetch $FETCH_POLICY_URL"
 
-    sh "$tmp/install" "$ROOT" > "$tmp/written"
+    sh "$tmp/fetch-policy" "$ROOT" > "$tmp/written"
     commit="$(head -n 1 "$tmp/written")"
     paths="$(tail -n +2 "$tmp/written")"