pico2_etm_trace: RP2350 board on the MIPI-20 ETM trace carrier

Board files for the trace carrier (console GP12/13, LED GP10, I2C GP8/9,
PIO-USB host on GP20, all retargeted in board.cmake so the SDK defaults
cannot mux a trace pin), compile-time trace pin-conflict checks, the
measured DBGPAUSE rationale, Ozone project, and skill/docs updates.
Trace validated at the stock 150 MHz (75 MHz TRACECLK, +1 ns sampling):
zero overflow through a 15 s throughput soak; V2 probe ceiling 120 MHz.

1 files changed, 1 insertions, 0 deletions

diff --git a/tools/build.py b/tools/build.py
index 0bb366e3d..aa8868cb8 100755
--- a/tools/build.py
+++ b/tools/build.py
@@ -34,6 +34,7 @@ ci_skip_boards = {
         'adafruit_fruit_jam',
         'adafruit_metro_rp2350',
         'feather_rp2040_max3421',
+        'pico2_etm_trace',
         'pico_sdk',
         'raspberry_pi_pico_w',
     ],