Rename the scripts that update the policy files

script/commit-current-upstream-policy-docs is now
script/write-upstream-policy-files: it writes the policy files and
commits nothing. script/update-policy is now
script/commit-upstream-policy-files, and make update-policy is now
make commit-upstream-policy-files. test/update-policy.sh follows.
Behaviour is unchanged.

Model: opus-5-5

README.md

@@ -119,7 +119,7 @@ alpine. We provide:
 - `script/test` —
   `docker build --build-arg CACHEBUST="$(date +%s)-$$" --target test --output type=cacheonly .`,
   building the `test` phase of the `Dockerfile`, which runs
-  `test/update-policy.sh`, without writing an image
+  `test/commit-upstream-policy-files.sh`, without writing an image
 - `script/lint` —
   `docker build --build-arg CACHEBUST="$(date +%s)-$$" --target lint --output type=cacheonly .`,
   building the `lint` phase, which runs prettier over the markdown files,
@@ -141,14 +141,14 @@ alpine. We provide:
   `script/check`
 - `script/install-precommit` — installs the git pre-commit hook (our own
   extension); `make hooks` shims to it
-- `script/commit-current-upstream-policy-docs` — fetch the vendored policy files
-  from this repo over HTTP and write them into a repo (our own extension). It
-  writes into the repo given as its argument, or its own repo with no argument.
-  It stops when its target is this repo.
-- `script/update-policy` — fetch the current
-  `script/commit-current-upstream-policy-docs`, run it on its own repo and
-  commit the result without pushing (our own extension). It is for the repos
-  that vendor the policy files. It stops when run here.
+- `script/write-upstream-policy-files` — fetch the vendored policy files from
+  this repo over HTTP and write them into a repo (our own extension). It writes
+  into the repo given as its argument, or its own repo with no argument. It
+  stops when its target is this repo.
+- `script/commit-upstream-policy-files` — fetch the current
+  `script/write-upstream-policy-files`, run it on its own repo and commit the
+  result without pushing (our own extension). It is for the repos that vendor
+  the policy files. It stops when run here.
 
 `make hooks` installs the pre-commit hook that runs `script/precommit`.