v0.254.0 — the saved notes follow the language, and the switch becomes a globe (R-557 slice 2 release C; SLICE 2 CLOSED)

The notes a background run SAVES — last night's backup line, the last error, the proof
result, the restore outcome — are written in the BOX's language at the moment they are
written. A household that switches sees the previous run's note in the old language until
the next run rewrites it: the operator's §16 option 1, stated rather than hidden.
EndRestoreOp no longer receives a Hungarian literal from anywhere.

The language switch is a globe. Two text links wrapped in the sidebar footer and asked the
reader to recognise "Magyar"/"English" as links; a globe is the one symbol every web user
already reads as "language", so nobody has to read Hungarian to escape Hungarian. It is
<details>/<summary> — a menu with no script, drawn inline because the icon sprite lives
only in layout.html and the visitor pages have their own shell.

Those visitor pages get the same globe, and a visitor's choice stays theirs: a display-only
felhom_lang cookie that langFor reads ONLY when there is no session. A signed-in household
can never inherit a language a previous visitor picked in the same browser. POST /lang is
CSRF-exempt for a narrow reason written at the exemption — its only achievable effect is the
language of the page the victim's own browser shows them — and safeBackPath refuses
//evil.example as well as https://, because "starts with /" alone is not the test. §16 taken:
a successful claim carries the cookie into the household's setting.

TWO PARITY EXCEPTIONS, MEASURED: 106 fixtures compared with a real diff — exactly two change
shapes (the dashboard footer, the globe in the shells) and 5 byte-identical, which are the
three pages that must not change.

I INTRODUCED A DEADLOCK AND THE SUITE CAUGHT IT BY HANGING. UpdateOffboxStatus holds the
settings write lock while running its callback; boxLang() wants the read lock; sync.RWMutex
is not reentrant. On a real box an off-site run would have hung forever HOLDING the settings
lock. Fixed by resolving the language before the callback, and guarded by a test that names
the file and line in a second instead of hanging for 25 minutes.

MinAgent: 0.131.0 (unchanged). No hub release needed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/web/r358_r360_handlers_test.go

@@ -80,8 +80,10 @@ func TestR358_PlaceHandlerRefusesIncompleteScratch(t *testing.T) {
 	s.offboxPlaceHandler(w, req)
 
 	loc := w.Header().Get("Location")
-	if !strings.Contains(loc, "nem+teljes") && !strings.Contains(loc, "nem%20teljes") {
-		t.Fatalf("a direct POST over a part-copy was NOT refused server-side; redirect was %q", loc)
+	// The flash carries a KEY since v0.252.0; resolved here the way the page resolves it, so the
+	// assertion is still about the SENTENCE the customer reads.
+	if !strings.Contains(flashSentence(t, loc), "nem teljes") {
+		t.Fatalf("a direct POST over a part-copy was NOT refused server-side; redirect was %q -> %q", loc, flashSentence(t, loc))
 	}
 	if m.RestoreStatus().Running {
 		t.Fatal("the place operation actually STARTED over an incomplete scratch")
@@ -101,8 +103,8 @@ func TestR358_ReconstituteHandlerRefusesIncompleteScratch(t *testing.T) {
 	s.offboxReconstituteHandler(w, req)
 
 	loc := w.Header().Get("Location")
-	if !strings.Contains(loc, "nem+teljes") && !strings.Contains(loc, "nem%20teljes") {
-		t.Fatalf("the DESTRUCTIVE restore was not refused over a part-copy; redirect was %q", loc)
+	if !strings.Contains(flashSentence(t, loc), "nem teljes") {
+		t.Fatalf("the DESTRUCTIVE restore was not refused over a part-copy; redirect was %q -> %q", loc, flashSentence(t, loc))
 	}
 	if m.RestoreStatus().Running {
 		t.Fatal("the destructive restore actually STARTED over an incomplete scratch")