Add named test points for power, key signal nodes, and vactrol drive currents

[NeoRecasata]

Same suggestion as the other module deep-dives. No test pads currently on the schematic. Calibration (especially after #2 makes R10 a trim) and debugging require clipping onto component leads.

Suggested test points

Power rails:

• TP_GND × 2 (one each on Board A and Board B)
• TP_+12V, TP_−12V (post reverse-polarity diode swap from Replace silicon reverse-protection diodes (D7/D8) with Schottky #4)

Signal path (on Board A):

• TP_Dry — input buffer output (U1A)
• TP_Xformer_out — transformer secondary post-HPF (U1B output)
• TP_Opto_in — opto-sat U2A input
• TP_Opto_out — opto-sat U2B output (right before C3 AC coupling)
• TP_Wet — wet signal post-AC coupling, going to U4A
• TP_Mix_pre_clip — wet/dry mix before diode clipping
• TP_Mix_post_clip — final output before exit jack

Vactrol drive (essential for #2 calibration):

• TP_Opto_LED — voltage across vactrol U3's LED (helps tune R10 trim)
• TP_Mix_LED — voltage across vactrol U6's LED (Mix CV processing health)

Action

• Add TPs to rev 0.7 schematic and PCB
• Optional: silkscreen labels on the PCB so you don't need to consult the schematic to find them