GNU Chess low-memory native acceptance

Tested binary SHA-256:
796ba70122e22276bbeac16ef55fa9bed87d525419072446df3afff6137d5c62

Matched native Perf Fixed Memory readout:
                         Before Chess   With Chess   Increase
Original 676b release       250.8 KiB     507.1 KiB   256.3 KiB
Low-memory 796b build       250.8 KiB     430.5 KiB   179.7 KiB
Measured fixed-memory reduction: 76.6 KiB (about 77 KiB).

Read-only native handle-table snapshots show all 29 C code resources 26-54
actually swapped out, with the fixed flag clear and lock count zero, at
idle both before and after GeoWrite and GeoDraw were loaded. The game then
reloaded code successfully, accepted e2e4, replied b8c6, and completed a
depth-four search returning b1c3. Raw guest-memory dumps are not included.

A second icon launch was refused by the native already-running dialog.
The existing game survived. F3 closed it to GeoManager, and reopening
started a fresh game at depth two.

Runtime: supplied English GeoWorks Pro 1.2, supplied 1024x768 TrueColor
driver, DOSBox Staging 0.83.0, 32 MiB RAM, and 1,500 handles. Symbol Editor
and the friend's German installation were unavailable. Separate 2 MiB
pressure evidence is supplied by the other native test owner. These
results do not establish a minimum RAM requirement.
