Draw the mode header once when initializing a non-WGN mode

[xmutantson]

Symptom: after the simulator initializes with a mode other than WGN selected (seen with MPG), the front panel shows the mode and S:N header lines twice - four header rows instead of two. The Lvl and CF lines below are unaffected. The duplicate clears on the next mode or parameter redraw, so it is cosmetic, but it recurs.

Root cause: in the mode-screen refresh in loop(), the WGN branch condition is (intMode == 0) || (! blnInitialized) - any uninitialized state selects the WGN branch regardless of the actual mode. When initializing into MPG (or MPM/MPD), that branch prints the mode + S:N pair, and the mode-specific branch then prints the same pair again. There is no screen clear or cursor reset between the two branches, so the second copy lands two text rows lower instead of overwriting.

Fix: select the WGN branch on the mode alone. Initialization of a non-WGN mode falls through to its own branch and draws the header exactly once; WGN behavior is unchanged (its own initialization path still runs identically).

One line changed; no functional/DSP behavior affected - display only.

[xmutantson]

Superseded by the consolidated correctness PR #5, which retains this duplicate-header cleanup and combines it with the required serial-control, state-reporting, maintenance, testing, and build-attestation changes.