A saved config was one JSON file; --config/--save let you keep several by juggling
paths. A template is the same content under a NAME, in a known place, with list, load
and delete — so "the LongCat long-shot setup" or "the quick 480p draft" is something you
pick rather than a path you remember.

Two properties beyond convenience:

- A template is a COMPLETE configuration — every CONFIG_FIELDS key, 66 of them — not a
  patch. Loading one therefore cannot leave an option from the previous run in place.
- The name is a SECURITY boundary, because names arrive from the CLI and from a browser.
  _safe_template_name strips separators and traversal and refuses a name with nothing
  usable; a test asserts that whatever is asked for, the resolved path stays inside the
  templates directory. "../../etc/passwd" becomes "etc-passwd".

They live at <out_dir>/templates/<name>.json, because that is the directory the launcher
already maps and persists — a template written to a container-local path would vanish on
the next run.

CLI: -T/--template NAME (layered over --config; explicit arguments still win, so a
template can be a base you tweak per run), --save-template, --list-templates (with date,
video model and option count), --delete-template. --config/--save are untouched.

Web: GET /templates, POST /templates/load, POST /templates/delete, and a picker on the
Run page with Load / Save as… / Delete. Saving is handled INSIDE /save-config rather than
in its own route, so the large form-to-config mapping is not duplicated and cannot drift
— a test pins that. Loading applies to default_args exactly as /save-config does, since
the Run page renders from it and a load that only wrote a file would appear to do nothing
until restart; it asks for confirmation first, because replacing every option is not an
undoable click.

A corrupt template is listed with its error rather than hiding the rest of the picker.

39 tests. Verified live against the web UI: save, list, load, delete, a missing name, and
a traversal attempt contained.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY