proto-p10: BX P merge case + silent variant for probe lookups

[MrLenin]

Summary

Two related fixes for cmd_bouncer_transfer's BX P handler in src/proto-p10.c.

1. GetUserN_silent() variant — stop spamming "couldn't find user!" snotices from BX P probes

Factor the existing GetUserN lookup into a private GetUserN_impl(numeric, quiet) helper. Expose two variants:

• GetUserN — original behaviour, every failure mode (numeric too long/short, server not found, user not found at valid slot) logs LOG_WARNING.
• GetUserN_silent — same lookup, all warnings suppressed on miss.

Flip only the two probe lookups in cmd_bouncer_transfer (old_primary and new_node) to the silent variant — the BX P handler is the probe path, so a lookup miss is expected, not bug-worthy. Everything else (mod-snoop / mod-track / opserv command targets / FAKEHOST / MARK / channel-mode victims) keeps the noisy GetUserN.

Symptom this addresses: networks running the IRCv3 fork's bouncer subsystem were seeing repeated

x3 warning: GetUserN(GkAAp) couldn't find user!

snotices to oper channels for every BX P probe miss.

2. BX P merge case for in-place conversion

The original handler logged a warning and bailed when both old_primary and new_node existed locally. Modern fork peers can emit BX P in exactly that shape when an N-introduced client is being absorbed into an existing primary on the same account — typically because burst ordering caused us to receive the would-be-alias's N before its BX C, so both userNodes landed in our tables.

Add a merge branch gated on same-handle:

if (new_node) {
    if (old_primary->handle_info
        && old_primary->handle_info == new_node->handle_info) {
        DelUser(old_primary, NULL, 0, "Bouncer transfer");
        return 1;
    }
    /* mismatched/no handle → keep original "log and ignore" */
}

DelUser(announce=0) suppresses both QUIT and KILL emission — this is internal cleanup, the network shouldn't see the alias's identity leave. The surviving identity is new_node.

The mismatched-handle case keeps the existing "log and ignore" guard — we don't silently merge across unrelated accounts.

Test plan

• X3 rebuilds clean, links to nefarious without warnings
• Silent variant verified: BX P probe path no longer emits GetUserN(...) couldn't find user! for the alias/primary lookups
• Mismatched-handle guard preserved: the genuinely-unexpected case still warns

Real-world burst-ordering scenario (modern fork peer sending BX P in merge shape) needs network-level verification on the fork side once both halves of the patch are in.

🤖 Generated with Claude Code