Console prompt: identity/machine both sides once redirected off Hera

sk_console_user_prefix() (repl.c) previously always returned "zuse"
(or the WIREBIND-attached username) as the left side of the bracket
prefix, regardless of which VM the console was actually pointed at --
"[zuse@rajames]" after USE rajames, always showing the authenticating
superuser rather than the active identity.

Changed on Captain Bob's direct instruction: once the console is
redirected into a WIREBIND identity's own console VM
(console_get_vm_name() != "Hera"), show that same name on both sides
-- "[rajames@rajames]" -- since WIREBIND births the console VM
literally named after the identity, so the identity IS that VM, not a
separate label. At the top level (still on Hera, nothing has
redirected yet), the original zuse_session/WIREBIND-username logic is
unchanged.

An earlier, more ambitious attempt (separate identity/machine tracked
state across every console_set_vm_name() call site) regressed live to
a wrong [zuse@Artemis] prompt and was fully reverted before reaching
any acceptance run -- the landed fix needed none of that new state,
just this one function.

Verified live on all three architectures: [zuse@Hera] at the top
level and after a live WIREBIND attach (before USE), [rajames@rajames]
after USE rajames, with task 3.9's Stage D relay still firing
correctly on top of it. Zero UNKNOWN WORD, dict_hash unaffected
(display-only change).

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

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