probes: add probe-config profiles loaded from probes.yaml

- new modules/probes/ parses probes.yaml (libyaml): a defaults: map
  applied on every jtag_open + named profiles: selected with
  `jtag_open <idx> <profile>` (jtag_profiles lists them); each value is
  pushed into the script envvar store the driver reads at open time
- ships a flashpro profile (ADBUS4 high-Z) that lets the IGLOO2 kit's
  embedded FlashPro (FT4232H, port 0) detect the chain
- CLAUDE.md: decision entry for probes.yaml + a design note on the
  probe / JTAG-link / device config strategy (driver-neutral link layer)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

probes.yaml

@@ -0,0 +1,27 @@
+# bs_explorer probe-config profiles
+#
+# Loaded at runtime by modules/probes/, layered on top of the built-in
+# config.script defaults. Looked up CWD-relative (run from the repo
+# root), or via $BS_PROBES.
+#
+#   defaults:  applied on every `jtag_open` (restores a known baseline
+#              so opening without a profile is deterministic).
+#   profiles:  named override sets; select with `jtag_open <idx> <name>`.
+#
+# Each key is a probe variable (see modules/config/config.script for the
+# full list); each value is what `set <KEY> <value>` would assign.
+
+defaults:
+  # Baseline for a standalone FT2232H JTAG probe: drive ADBUS4 as the
+  # "JTAG buffer enable" output (matches the built-in default).
+  PROBE_FTDI_SET_PIN_DIR_ADBUS4: 1
+
+profiles:
+  # Embedded FlashPro on Microsemi eval kits (FT4232H, JTAG on channel A
+  # = probe index 0). Its ADBUS4 must be left high-Z or the chain stays
+  # silent. Usage: jtag_open 0 flashpro
+  flashpro:
+    PROBE_FTDI_SET_PIN_DIR_ADBUS4: 0
+
+  # Plain FT2232H probe: nothing to override beyond the defaults.
+  ft2232h: {}