BSDL: ingest libbsdl into essim and populate PinSpec from a device model

Link libbsdl dynamically (add_subdirectory ../libbsdl, overridable via
-DBSDL_DIR). New BsdlModel wraps the C ABI and reduces a parsed .bsd to
essim's pin vocabulary; apply_bsdl() binds each port to a Pin (by name, then
by physical pad) and sets its spec: direction, function (TAP role / power /
ground / signal), pad, and source = Bsdl.

This feeds the PinSpec fields from P1, so verify's existing power/ground
placement pass now lights up for BSDL-modelled parts. Covered by
test_bsdl_apply (name + pad binding, TAP roles, linkage classification).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CMakeLists.txt

@@ -26,6 +26,14 @@ FetchContent_MakeAvailable(ftxui)
 find_package(libzip REQUIRED)
 find_package(pugixml REQUIRED)
 
+# libbsdl — standalone BSDL parser (LGPL-2.1), dynamically linked from essim
+# (EUPL-1.2, which the LGPL permits). Path overridable via -DBSDL_DIR=...;
+# its CLI and tests are not needed inside essim's build.
+set(BSDL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../libbsdl" CACHE PATH "libbsdl source tree")
+set(BSDL_BUILD_CLI   OFF CACHE BOOL "" FORCE)
+set(BSDL_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+add_subdirectory(${BSDL_DIR} ${CMAKE_BINARY_DIR}/libbsdl)
+
 # Library target = everything except main.cpp; reused by `essim` and `essim_tests`.
 file(GLOB_RECURSE LIB_SOURCES "src/*.cpp")
 list(REMOVE_ITEM LIB_SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/src/main.cpp")
@@ -39,6 +47,7 @@ target_link_libraries(essim_lib
     ftxui::component
     libzip::zip
     pugixml::pugixml
+    bsdl::bsdl
 )
 
 add_executable(essim src/main.cpp)