refactor(shared): split runResult out of runSubmit (RB-17)

runSubmit did two things at once: fold a call into a Result, and mint
an Idempotency-Key for it. Five call sites are reads and had no
business minting one — brief.adapter.ts:load, org-template.adapter.ts
:list/:load, and stamdata.adapter.ts:list/:load. stamdata.adapter.ts's
own docstring already said "Both endpoints are reads … There is no
write method" while both called runSubmit; that mismatch is the
sharpest evidence, and the reason the baseline's original "~13
mutations" count (derived from the helper's name, not the code) was
wrong by five in one direction.

Split submit.ts in place: runResult is the try/catch + problemDetail
fold with no mint; runSubmit is runResult wrapping
withIdempotencyKey. Zero behaviour change for the 8 real mutations
(brief save/submit/approve/reject/send/reset, org-template
save/publish/rollback) — same fold, same mint, same timing. The five
reads now run the fold with no pendingIdempotencyKey touched.

submit.spec.ts asserts the split behaviourally via
currentIdempotencyKey() (two reads inside the same call agree only
when a key was minted and reused) rather than mocking a relative
import, matching this repo's existing vitest convention. Verified red
without the fix by temporarily reintroducing the mint into runResult.

ApplicationsStore.cancel/AdminCasesStore.delete (RB-20) and
FeatureFlagStore.set are out of scope and untouched — the latter
already calls runSubmit correctly.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

libs/shared/docs/behaviour-spec.mdx

@@ -20,7 +20,7 @@ tested where._
 
 Every bullet below is a real test name from the suite — an `it()` title (frontend) or a test
 method name (backend), read as a sentence. Nothing here is hand-written prose: this page
-**is** the suite, reshaped for a business reader. 440 frontend behaviours across
+**is** the suite, reshaped for a business reader. 445 frontend behaviours across
 9 contexts; 231 backend behaviours across 39 test
 classes.
 
@@ -800,11 +800,19 @@ classes.
 
 - leaves an unrelated endpoint untouched
 
+#### runResult
+
+- folds a resolved call into ok(value)
+- maps a ProblemDetails rejection to err(detail)
+- falls back when the rejection has no detail
+- mints no Idempotency-Key — the read fold
+
 #### runSubmit
 
 - folds a resolved call into ok(value)
 - maps a ProblemDetails rejection to err(detail)
 - falls back when the rejection has no detail
+- mints exactly one Idempotency-Key for the whole call — the write fold
 
 #### satisfaction helpers