FTS-4001 §4 specifies `^AFLAGS flag_string`, space-separated, no
colon. fmail's jamfun.c:321 ("FLAGS ") and ftr.c:113
("\1FLAGS DIR\r") both emit the same form; HPT's ctrl-buffer
parser accepts it verbatim without a colon.
BuildKludgePrefix was previously emitting `^AFLAGS: DIR` with a
colon, which caused consumer parsers (NR's ParseKludges, HPT's
getFlags, fmail's getKludge) to miss the FLAGS kludge entirely.
In NR that manifested as FLAGS DIR / IMM routing being silently
ignored -- the message would fall into normal routing instead of
direct/immediate delivery, and the outbound pkt's destination
node ended up unset (from the route resolver rather than the
message's actual destination).
One-line fix: drop the colon, keep the rest of the kludge
emission unchanged. MSGID: / REPLY: / PID: / CHRS: / TZUTC:
keep their colons per their respective specs (FTS-0009, FRL-1028,
FSC-0054, FSC-0093).