6b4b7647e fixed this for synapse-usage-exporter only. A checkout owned by
a different user makes the git task fail from then on, either with a
permission error or with git's dubious-ownership protection, until
someone removes the directory on the host by hand. It gets into that
state when the matrix user's uid changes (a server migration or a restore
onto a differently numbered user), when an earlier clone ran as another
user, or when someone runs git as root inside the checkout.

Every other role cloning a repository onto the server was open to the
same failure, so ensure the checkout's ownership recursively before
updating it at the remaining 54 sites.

The three matrix-synapse ext clones also gain force=yes. They were the
only on-server clones without it, which left a checkout that an
interrupted run had half-written wedged, instead of repaired on the next
run.

matrix-matrixto used to clone as root into a directory that nothing ever
chowned, unlike every other role. It now becomes the matrix user too.

The Element Web and SchildiChat Web theme checkouts live on the Ansible
controller, where correcting ownership is not ours to do, so they merely
mark the checkout as a safe directory for git.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

The variable was defined, but the configuration template hardcoded the
command prefix, so changing the variable had no effect.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Part of adopting a uniform naming policy for bridge variables,
where the variable prefix matches the role directory name.

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