fix(view): a started run's configuration can be read in full

Closes #16 (closed). A started run's Configure dialog disabled its whole form; a disabled scroll area does not scroll, and Edit YAML was disabled with it, so a long configuration could not be seen.

• The scroll area stays live; _lock_fields makes each field read-only (text, numbers) or disabled (choices, list +/- buttons).
• Edit YAML… becomes View YAML… and opens the run's file in YamlDialog(read_only=True): no editing, Close only.
• Save still changes nothing for a started run (unchanged test).

New GUI test test_a_started_run_can_be_read_in_full.