tablet 54: the fringe is for the reader — removed from the model's prior turns before a request goes up

The gate sews its fringe into the delivered reply; the client keeps that
reply as the assistant's turn; the next request carries it back up
inside the model's own history with nothing to say it was added. The
builder's session, behind the gate since this afternoon, ended five
replies in a row with a forged fringe (tablet 53's form), one of them in
the message that promised not to. Bamidbar 15:39: the fringe is seen by
the wearer, the reader — before the model's eyes it is a template.

Shape.unfringed/2 removes every line in the gate's voice (its fringe, a
forgery, the stream's "not examined") from assistant turns; Gate.pass
and Gate.Stream.pass apply it before forwarding, so the rebuke body
inherits it; the caller's turns stay as given; a turn that would be left
empty is left as it came. strip_forged/1 now also strips the stream's
"not examined" line. Tests: Shape.unfringed on both shapes and the edge
cases; the forwarded first and rebuke bodies carry no fringe; the fake
upstream echoes if a fringe reaches it in history and the stream pass
proves it does not. Elixir 622 / 0 failures.

Specs: broken tablets 54, bishe'arecha §III status, Tamid gate contract
and forged_fringe note, KOHEN gate paragraph.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

KOHEN.md

@@ -570,8 +570,10 @@ the gate scenario without echoing it (`~/.config/bikoret/upstream_keys`,
 
 A caller can put Bikoret between themselves and a model instead of
 bringing the output by hand: point the model's own client at the gate
-and add the courtyard key. The request goes through unchanged under the
-caller's own model key (never stored, never logged); the reply comes
+and add the courtyard key. The request goes through under the caller's
+own model key (never stored, never logged), unchanged but for the
+fringes of earlier replies, which the gate removes from the model's own
+turns before the request goes up (tablet 54); the reply comes
 back examined, with the fringe on its last text block, the headers
 `X-Bikoret-Bedikah` / `X-Bikoret-Verdict`, and a `bikoret` object.