Track the x32 xy_microsteps default in forgetest and the bench tools

Acceptance baseline: XY_MODE_DEFAULT 8 -> 32, split out XY_MODE_BASE (8) for
the tick/ramp scaling, matching the driver. The mode-aware comparisons
(fixed_sysfs of the resolved mode) judge an unset machine at x32.

Host CI: xy_mode_test.py default and invalid cases expect x32/213.333/112640.

Bench tools: raster_dry.py and xy_pattern_accel.py set_mode() cleared the key
for mode 8, which relied on clear == the x8 default; clearing now yields x32,
so they set the mode explicitly and restore to x32. live_fire_drills
STREAM_RATE_HZ is the 28160 Hz laser reference tick, the same at every mode.

scripts/bench/live_fire_drills.py

@@ -655,7 +655,7 @@ def drill_pthresh(g):
 DLADDER_PCT = (1, 2, 5, 10, 20, 40, 70, 100)
 DLADDER_LEN = 25.0                      # mm of burn per rung
 DLADDER_PITCH = 3.0                     # mm between rungs
-STREAM_RATE_HZ = 28160                  # machine tick (GFSINK_RATE default)
+STREAM_RATE_HZ = 28160                  # the 28160 Hz laser reference tick (the same at every microstep mode)
 PWM_PERIOD = 127                        # 7-bit power byte against PWMSAR
 CONF = os.environ.get('GFHOME_CONF') or '/data/forgefirm/forgefirm.conf'
 PULSE_MIN_KEY = 'laser_pulse_min_ticks'