bsdl: extract parser into standalone libbsdl, pulled via FetchContent

The BSDL loader (seeded from the Viveris parser) now lives in its own
LGPL repo, electronics/libbsdl, consumed with CMake FetchContent.
Local development override: -DFETCHCONTENT_SOURCE_DIR_BSDL=<path>.
src/modules/bsdl_parser/ is removed; callers go through the libbsdl
API. Build verified against the libbsdl checkout.

CLAUDE.md

@@ -20,7 +20,12 @@ other families (Lattice, Microsemi, …) by playing a vendor-exported SVF.
 The Viveris library itself lives unchanged in `src/modules/`. Everything
 new is in `src/bs/` (the REPL) and the project modules (`target/`,
 `bscan/`, `spi_flash/`, `svf/`, `probes/`, `program/`, `arm_debug/`)
-sitting alongside the Viveris ones.
+sitting alongside the Viveris ones. The BSDL parser was extracted into
+a standalone library, **[libbsdl](ssh://gitea@git.beafrancois.fr:8329/electronics/libbsdl.git)**
+(LGPL, seeded from the same Viveris loader), and is now pulled in via
+CMake `FetchContent` instead of vendored. To build against a local
+checkout (e.g. side-by-side dev): configure with
+`-DFETCHCONTENT_SOURCE_DIR_BSDL=/path/to/libbsdl`.
 
 ## Architecture
 
@@ -30,13 +35,14 @@ src/
 └── modules/
     — Viveris's library (LGPL, unchanged) —
     ├── jtag_core/         TAP state machine, IR/DR shifts
-    ├── bsdl_parser/       .bsd loader
     ├── bus_over_jtag/     SPI/I²C/MDIO/parallel mem bit-bang over EXTEST
     ├── drivers/           FTDI, J-Link, Linux GPIO, LPT, Digilent (optional, dlopen)
     ├── script/            Script engine (the real UI)
     ├── config/            Built-in config.script
     ├── os_interface/      Portable fs/network wrappers
     └── natsort/           Natural pin-name sorting
+    — pulled via FetchContent (LGPL, separate repo) —
+    └── (libbsdl)          BSDL (.bsd) parser; struct + JSON; stable C ABI
     — new (this project) —
     ├── target/            Target registry: FPGAs + CPUs (parses data/targets.yaml)
     ├── bscan/             JTAG TAP primitives (set_ir/shift_ir/shift_dr/tap_reset/
@@ -528,7 +534,11 @@ mkdir build && cd build && cmake .. && make
 Build needs **libyaml** (pkg-config `yaml-0.1`; Arch `libyaml`, Debian
 `libyaml-dev`) for the registry, and **libftdi1** + **libusb-1.0**
 (pkg-config `libftdi1`; Arch `libftdi`, Debian `libftdi1-dev`) for the
-FTDI/Olimex driver. Run `bs` from the repo root so it finds
+FTDI/Olimex driver. **libbsdl** (the BSDL parser, separate repo) is
+pulled in by CMake `FetchContent` at configure time — needs network on
+first build. For a local checkout, configure with
+`-DFETCHCONTENT_SOURCE_DIR_BSDL=/path/to/libbsdl` (built-in FetchContent
+override, no clone happens). Run `bs` from the repo root so it finds
 `data/targets.yaml` (and `data/bsdl_files/`, `data/bscan_proxies/`), or
 point `$BS_TARGETS` at it.