molecule-shared/ and the workflow itself are used by every scenario, so a
change to either has to run all of them rather than only the roles whose own
files moved. They were also missing from the paths filter, so such a change
would not have triggered the workflow at all.

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

The previous commit moved requirements.txt into molecule-shared/ but left
the workflow installing from the old per-role path, so CI failed on a file
that no longer exists while the local run - which reads the shared file
through bin/molecule.sh - passed.

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

Not for merging as-is. One role's scenario plus the workflow that would
make per-role testing affordable here, so we can see how it behaves before
deciding whether to do the other 69.

Unlike the MASH repositories, one repository holds every role, so running
everything on every push is not an option. The workflow's first job works
out which roles a push touched and builds the matrix from that; a change to
docs, or to a role with no scenario yet, runs nothing.

Three things this role needed that a MASH role does not:

- The variables matrix-base would supply (matrix_base_data_path,
  matrix_domain, matrix_user_name, matrix_group_name and the uid/gid) have
  to be provided by the scenario, and the user and group have to exist
  before the role's file tasks run.
- The service contacts the homeserver while starting up - it fetches
  /_matrix/client/v3/joined_rooms to resolve its room mapping and exits 1
  if that fails - so prepare.yml stands up a stub homeserver. Most roles
  here are bridges and bots, so this is likely the rule rather than the
  exception.
- verify.yml runs as its own play, where role defaults are out of scope, so
  the paths it reads are pinned in molecule.yml. The version is deliberately
  NOT pinned: it is read from defaults/main.yml so the assertion compares
  the running image against what the role ships.

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