verify: JTAG boundary-scan chain integrity (flagship)

New check_jtag_chain(System*): collects TAP pins by PinSpec.function, resolves
each to its net, and flags JtagTapIncomplete (a device missing TDI/TDO/TMS/
TCK), JtagBusUnbridged (TMS or TCK not common to every TAP device), and
JtagChainBreak (dangling TDO/TDI, chain fan-out, or not a single head->tail
daisy chain). Surfaced as a pass in `verify`; AnomalyKind extended. Covered by
test_bsdl_check (healthy chain, broken chain + split bus, incomplete TAP).

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

src/system/bsdl_check.hpp

@@ -16,4 +16,13 @@ class System;
 // un-modelled parts).
 std::vector<Anomaly> check_pin_specs(System *sys);
 
+// JTAG boundary-scan chain integrity, using pins whose PinSpec.function is a TAP
+// role (JtagTdi/Tdo/Tms/Tck/Trst). Resolves each TAP pin to its net and checks:
+//   - JtagTapIncomplete : a TAP device missing TDI/TDO/TMS/TCK;
+//   - JtagBusUnbridged  : TMS or TCK not common to every TAP device;
+//   - JtagChainBreak    : the TDO→TDI daisy chain dangles, fans out, or is not a
+//                         single path (≠1 head / ≠1 tail).
+// Empty when the system has no TAP pins.
+std::vector<Anomaly> check_jtag_chain(System *sys);
+
 #endif // _BSDL_CHECK_HPP_