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/svf/svf.h

@@ -0,0 +1,40 @@
+#ifndef _SVF_H
+#define _SVF_H
+
+#include "jtag_core/jtag_core.h"
+
+/*
+ * SVF player (single-device chain).
+ *
+ * Plays a standard subset of Serial Vector Format over the currently
+ * open probe, using the bscan_* TAP primitives. SVF is what Libero,
+ * Diamond/Radiant, Vivado, … export with the vendor programming
+ * algorithm already baked in, so one player programs many targets with
+ * no per-vendor code.
+ *
+ * Supported: SIR / SDR with TDI/TDO/MASK/SMASK and a masked TDO compare;
+ * RUNTEST (TCK/SCK counts and SEC delays); STATE (RESET / IDLE);
+ * ENDIR / ENDDR (IDLE only); HIR/HDR/TIR/TDR (length 0 only); TRST;
+ * FREQUENCY. SMASK is parsed but not applied.
+ *
+ * Not supported (single-device tool): non-zero header/trailer scans
+ * (multi-device chains) and non-IDLE stable end states — both rejected
+ * with a clear error.
+ *
+ * log() receives progress / error lines (is_error != 0 on failure).
+ * Returns 0 on success, < 0 on parse error or a TDO compare mismatch.
+ * stats may be NULL.
+ */
+
+typedef void (*svf_log_fn)(void *user, int is_error, const char *msg);
+
+typedef struct {
+    long commands;     /* commands executed */
+    long scans;        /* SIR + SDR */
+    long compares;     /* TDO compares performed */
+} svf_stats;
+
+int svf_play_file(jtag_core *jc, const char *path,
+                  svf_log_fn log, void *user, svf_stats *stats);
+
+#endif