the log day now starts at 6am, because the playtesters are night owls

A midnight boundary splits one evening across two files at exactly the moment
the session is most worth reading whole: the 01:30 crash lands in a different
file from the 23:00 run that set it up. And a 02:00 session is "last night" to
everyone who was in it, so filing it under the new calendar date reads wrong
even when nothing goes bad.

So shift the clock back 6h before taking the date for the FILENAME. The log day
runs 06:00 -> 06:00 and one night stays in one file.

Only the filename moves. The session header and the lastrun breadcrumb each
call GetLocalTime separately (three distinct SYSTEMTIMEs in this function), so
every timestamp a human reads is still true local time -- checked the scoping
rather than assuming it, since sharing one variable would have silently
backdated the header by six hours.

FileTimeToSystemTime carries the month and year boundaries, verified against a
scratch harness rather than reasoned about:

  2026-07-28 20:00 -> solo_20260728.log     one playtest night,
  2026-07-28 23:59 -> solo_20260728.log     start to finish,
  2026-07-29 00:01 -> solo_20260728.log     in a single file
  2026-07-29 05:59 -> solo_20260728.log
  2026-07-29 06:00 -> solo_20260729.log     the boundary
  2026-08-01 01:00 -> solo_20260731.log     month
  2027-01-01 03:00 -> solo_20261231.log     year
  2026-03-01 02:00 -> solo_20260228.log     non-leap February

Nothing in the tooling parses these filenames -- the operator app's own log is
operator_relay.log and _collect_egg is mission settings, not logs -- so the
console auto-transfer is unaffected.

The player-facing text did need fixing though: the bats and README told players
to send the log "dated today", which is now wrong for anyone who plays past
midnight. They now say to take the NEWEST one and ignore the date, with a note
on why. That was already the safer instruction.

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

game/btl4main.cpp

@@ -605,6 +605,35 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
 			SYSTEMTIME lt;
 			GetLocalTime(&lt);			// NOT cmd's %DATE%: locale-ordered, and
 										// on en-US it contains '/' (path chars).
+
+			// THE LOG DAY STARTS AT 06:00 LOCAL, NOT MIDNIGHT.  Playtests run
+			// late, and a midnight boundary splits one evening across two files
+			// exactly when the session is most worth reading whole -- the 01:30
+			// crash lands in a different file from the 23:00 run that set it up.
+			// (A 02:00 session is also "last night" to everyone who was in it,
+			// so a file named for the new calendar date reads wrong anyway.)
+			// Shift the clock back 6h before taking the date: the log day then
+			// runs 06:00 -> 06:00 and one night is one file.  Only the FILENAME
+			// is shifted -- every line inside still carries real local time, and
+			// the session header still records the true date.
+			{
+				const ULONGLONG LogDayStartHour = 6;
+				FILETIME ft;
+				if (SystemTimeToFileTime(&lt, &ft))		// pure arithmetic; no TZ
+				{										// conversion either way
+					ULARGE_INTEGER u;
+					u.LowPart  = ft.dwLowDateTime;
+					u.HighPart = ft.dwHighDateTime;
+					u.QuadPart -= LogDayStartHour * 3600ULL * 10000000ULL;	// 100ns
+					ft.dwLowDateTime  = u.LowPart;
+					ft.dwHighDateTime = u.HighPart;
+					SYSTEMTIME shifted;
+					// FileTimeToSystemTime carries month/year boundaries for us,
+					// so 01:00 on the 1st correctly names the previous month.
+					if (FileTimeToSystemTime(&ft, &shifted))
+						lt = shifted;
+				}
+			}
 			// SIZE ROLL-OVER -- never deletes anything, but keeps each FILE small
 			// enough to actually send.  A playtest evening concatenates into one
 			// file (4.3 MB from a single session in scratchpad/night5/), and the