svf: initial SVF player + svf_play command

New modules/svf/ plays the single-device SVF subset over the bscan_*
primitives: SIR/SDR with masked TDO compare, RUNTEST (TCK/SEC), STATE
(RESET/IDLE), ENDIR/ENDDR (IDLE only), HIR/HDR/TIR/TDR (length 0), TRST,
FREQUENCY. Exposed as `svf_play <file>`. It warms up the FTDI link
first — the MPSSE's first data read after open returns stale FIFO
content, normally hidden because jtag_scan runs before anything.

Also adds the bscan_tap_reset prototype. Validated on the live IGLOO2
M2GL010T: a hand-written IDCODE-check SVF passes (masked compare) and a
deliberately wrong one is caught at the mismatching bit. A generic
program dispatch off the prog tag, multi-device chains and non-IDLE end
states are still TODO.

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

modules/bscan/bscan.h

@@ -43,6 +43,9 @@ int bscan_shift_ir(jtag_core *jc, const uint8_t *tdi, uint8_t *tdo, int nbits);
 /* Emit `ncycles` TCK cycles while staying in Run-Test/Idle. */
 int bscan_idle_cycles(jtag_core *jc, int ncycles);
 
+/* Force Test-Logic-Reset (5 TCK with TMS=1) and land in Run-Test/Idle. */
+int bscan_tap_reset(jtag_core *jc);
+
 /* --- High-level operations ---------------------------------------- */
 
 /* Load a raw bitstream payload (no .bit container header) into the