fix(booth): a partial ask answer is recorded, not refused

Operator: the form failed when a question was left blank. Refusing the whole
submission over one blank threw away the picks that were made, and the HTML
`required` on the radios blocked it in the browser before the server saw it.

- answered questions recorded; blank ones land in `unanswered`; `complete` says
  whether the set is finished; a blank question carrying a note keeps the note
- `required` dropped from both templates so the browser cannot block a partial
- refused only when there is no pick anywhere AND no notes (a 400 — that would
  flip an open ask to answered with no decision recorded); a choice outside the
  option list is still an error
- new ◐ partial state with an n/N count; skipped questions render as skipped
- README + global CLAUDE.md tell reading sessions to check `complete`
- 154 tests; v0.1.15

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "booth"
-version = "0.1.14"
+version = "0.1.15"
 description = "The Booth — a dead-simple standing web server that scans a data dir of drop-folders and renders each as an ephemeral media 'booth' (image/webm/audio auto-gallery, or a folder's own index.html verbatim). Also accepts browser/curl uploads for pickup under a human-readable id. 24h TTL, then the folder is wiped. Fleet tool for CC sessions to surface A/B and smoke results to the operator."
 requires-python = ">=3.11"
 dependencies = [