Silence routine diagnostic noise; fix a real CRLF double-submit bug

Two separate fixes, found and closed together after task 3.9/prompt-
format landed (Captain Bob: "finish the work first then we'll do
cleanup before 3.10 begins").

1. Logging noise (confirmed live via QMP screendump): three sources
   were cluttering ordinary interactive console sessions.
   - INFERENCE "Output validation failed, ignoring results"
     (vm_runtime.c, kernel; vm_time.c, hosted mirror) and xhci "CSW
     status = FAILED"/"unit not ready -- retrying" (xhci.c) were
     already log_message(LOG_WARN/LOG_ERROR, ...) calls, just visible
     at the default runtime LOG_WARN level -- downgraded to LOG_INFO,
     all three fire routinely and self-resolve (xhci.c's own existing
     comment already documents the retry as expected SCSI UNIT
     ATTENTION behavior, not a driver defect).
   - Stadium: dispatch cell=... (stadium.c's stadium_dispatch()) was a
     genuine defect: an unconditional console_puts()/console_println()
     sequence with no level gating at all, printing on every single
     dispatch. Rewritten through log_message(LOG_DEBUG, ...).

2. CRLF double-submit (found while investigating why the cleaned-up
   noise still didn't look like a normal single-VM session):
   sk_console_readline() (repl.c) breaks on '\r' OR '\n' as independent
   terminators, so a line sent as both bytes submits twice -- the real
   line, then an immediate empty-line submit on the second byte, each
   printing its own " ok". Pre-dates Stage D entirely, not an async-
   relay artifact. Fixed with a single non-blocking peek-and-discard
   for the paired byte right where the line terminates.

Verified live on all three architectures for both fixes: zero UNKNOWN
WORD, dict_hash identical to every prior acceptance run in this
document (both changes are display/interaction-only).

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

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