fix(template_import): Remove silent template-dir fallback in ReplaceFiles offline path
When the workspace container is offline and writeViaEphemeral fails
(docker unavailable), ReplaceFiles previously fell back to writing
to the host-side template directory. This silently returned 200 with
"source: template" while the file change was invisible after restart
because the restart handler reads from the Docker volume, not the
template dir (issue #151).
Now returns 503 Service Unavailable with a message telling the caller
to retry after the workspace starts. The ephemeral write path is
the only correct mechanism for offline-container updates.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Molecule AI Core-BE
c9cf240751