fix(curation): exclude seed-process + chat-inbox + attendance contexts + startability QA

Oracle round-6 watch-out: 'Employee Onboarding' (a CANVAS_SEED_PROCESS
wizard-incomplete draft) was reaching the Assistant list because its
display_name passed the dev-artefact regex. EA2 runtime then returned
500 transaction_creation_failed because it lacked view/data attachments.

- flowCuration.NON_BUSINESS_SOURCE_CONTEXTS now drops CANVAS_SEED_PROCESS,
  CANVAS_SEED_STEP, CANVAS_CHAT_INBOX, CANVAS_ATTENDANCE_ROOT,
  CANVAS_ATTENDANCE_SITE - all internal canvas source_contexts.
- qa/full_dogfood.mjs new assertion 'assistant_list_processes_all_startable'
  posts each Assistant-listed flow to /api/runtime/transactions and
  asserts non-4xx/5xx response.

src/lib/flowCuration.ts

@@ -33,6 +33,11 @@ const NON_BUSINESS_SOURCE_CONTEXTS = new Set([
   "EA2_CHAT_MSG",
   "CANVAS_CHAT_THREAD",
   "CANVAS_CHAT_MSG",
+  "CANVAS_CHAT_INBOX",
+  "CANVAS_ATTENDANCE_ROOT",
+  "CANVAS_ATTENDANCE_SITE",
+  "CANVAS_SEED_PROCESS",
+  "CANVAS_SEED_STEP",
   "EA2_WIZARD_STEP",
   "EA2_DRAFT_PROCESS:process_creation",
 ]);