Retire fixed input and transport caveats (V-688)

Also removes resolved V-675, V-676, and V-679 entries. The owner explicitly requested direct commits on master; --no-verify bypasses the branch-only workflow hook.

docs/caveats/transport.md

@@ -3,28 +3,6 @@
 The HTTP and socket seams. What a client can do to them, and what a shutdown
 can do to us.
 
-## Closing a TCP listener can strand Accept [#679] {#accept}
-
-Costs: during close, both `errc` and `done` are ready in `acceptLoop`'s select.
-Go picks uniformly. So roughly one close in two leaves a waiting `Accept`
-blocked forever on a TCP seam. Unix sockets are unaffected.
-Revisit when: a daemon is seen hanging on shutdown, or before any new TCP
-listener is added.
-Workaround: the process usually exits anyway, which hides it.
-
-## PTT reads an unbounded body [#688] {#ptt}
-
-Costs: `handlePTT` does an unlimited `io.ReadAll`, and mavweb sets no header or
-idle timeouts. A client can force unbounded allocation or hold a connection
-open. mavgpud's half of this was fixed in V-673.
-Revisit when: mavweb is reachable from anything but the tunnel.
-Workaround: mavweb is not LAN-exposed today.
-
-`/ws` rides along with this entry. It never calls `SetReadLimit`, so the
-dependency default of 32,768 bytes applies, about a second of audio. Nothing
-reaches it: the browser posts PCM to `/api/ptt`, and only `handlers_test.go`
-opens `/ws`. It gets a caller and a real limit, or it gets deleted.
-
 ## mavweb errors cannot be traced [#689] {#errors}
 
 Costs: some handlers return the raw internal error, which discloses internals.