ipc: a seed_event method, step-up gated, refused by the store (V-518)

The pattern detector needs four events for one action+object spread by at
least two hours before it proposes a routine. The only writer in the tree is
a fact write at time.Now(), so V-43, V-46, V-247 and V-254 all stopped at the
same missing step. This is the wire half of the seam that unblocks them.

The request takes a fact — key, value, timestamp — not an event, so
pattern.Extract runs for real on the daemon side and a key the extractor
ignores seeds nothing. The response says which of those happened, because a
caller that assumed a seed always yields an event would read four silent
successes as a broken detector.

AuthStepUp, the same rung as mutating the tool allowlist, and not because
backdating is privileged in the usual sense: every other write records when
something happened and this one asserts it. StoreAPI refuses outright — the
method needs the daemon's detect-and-propose step, and a direct store caller
would write a fact and quietly skip it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011x5DgnExQ5XZy8TZPs5bot

internal/ipc/storeapi.go

@@ -265,6 +265,14 @@ func (a *storeAPI) TickTrace(ctx context.Context) (TickTrace, error) {
 	return TickTrace{}, errors.New("store: tick trace not available via direct store API")
 }
 
+// SeedEvent — same shape as MorningStatus: writing the fact is a store call,
+// but extraction and detect-and-propose live in mavend, and a seed that wrote
+// the fact without running them would be the one thing this seam must not be,
+// a way to prove a detector that never ran (Vikunja #518).
+func (a *storeAPI) SeedEvent(ctx context.Context, req SeedEventReq) (SeedEventResp, error) {
+	return SeedEventResp{}, errors.New("store: seed event not available via direct store API")
+}
+
 func (a *storeAPI) MorningStatus(ctx context.Context) ([]MorningRoutineStatus, error) {
 	return nil, errors.New("store: morning status not available via direct store API")
 }