- A per-source scan sends the source's public path; when the sources
changed since they were read the toast says the server's reason and
the list and saved values are read again.
- "watching until restart" for a source the running monitor still
watches after monitoring was saved off, and the status adds "Restart
ComfyUI to apply: Watch for new outputs." from restart_required_fields.
- A save refused for one unusable source marks that row and the status
is the server's message naming it.
- A valid configured source the effective list holds under another
spelling reads "same folder as another source".
- The busy toast names the job the 409 named (ApiError keeps a
validated running job and refused source), falling back to the list.
- The Add source dialog's listeners live on the page scope and Enter
adds; its markup is compared with the concept (D127).
- TESTING.md: D-NEW-S4-1 is D127; D-NEW-S4-2 records the new copy; the
Sources contract describes the lexical containment, invalid-source and
sources-changed.