svf: extract player core into standalone libsvf, keep bscan glue

The SVF player now lives in electronics/libsvf behind a five-function
JTAG ops table, shared with the wifi_jtag_programmer Zephyr firmware.
src/modules/svf/ shrinks to the bscan_*-backed port (bs_svf_play),
which also keeps the FTDI stale-FIFO warm-up. Local checkout override:
-DFETCHCONTENT_SOURCE_DIR_SVF=<path>.

src/modules/svf/svf_glue.c

@@ -0,0 +1,58 @@
+/*
+ * bs_explorer glue for libsvf: maps the svf_jtag_ops port onto the
+ * bscan_* TAP primitives.
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include <unistd.h>
+
+#include "svf_glue.h"
+#include "bscan/bscan.h"
+
+static int ops_tap_reset(void *ctx)
+{
+    return bscan_tap_reset((jtag_core *)ctx);
+}
+
+static int ops_shift_ir(void *ctx, const uint8_t *tdi, uint8_t *tdo, int nbits)
+{
+    return bscan_shift_ir((jtag_core *)ctx, tdi, tdo, nbits);
+}
+
+static int ops_shift_dr(void *ctx, const uint8_t *tdi, uint8_t *tdo, int nbits)
+{
+    return bscan_shift_dr((jtag_core *)ctx, tdi, tdo, nbits);
+}
+
+static int ops_idle_cycles(void *ctx, int ncycles)
+{
+    return bscan_idle_cycles((jtag_core *)ctx, ncycles);
+}
+
+static void ops_delay_us(void *ctx, unsigned long us)
+{
+    (void)ctx;
+    usleep((useconds_t)us);
+}
+
+static const svf_jtag_ops bscan_svf_ops = {
+    .tap_reset   = ops_tap_reset,
+    .shift_ir    = ops_shift_ir,
+    .shift_dr    = ops_shift_dr,
+    .idle_cycles = ops_idle_cycles,
+    .delay_us    = ops_delay_us,
+};
+
+int bs_svf_play(jtag_core *jc, const char *path,
+                svf_log_fn log, void *user, svf_stats *stats)
+{
+    /* Warm up the link before the first real scan: the FTDI MPSSE's first
+     * data read after a fresh open returns stale FIFO content. The normal
+     * Viveris flow hides this (jtag_scan/autoinit runs first); do a
+     * throwaway reset + DR read so a standalone svf_play is reliable. */
+    uint8_t junk[4];
+    bscan_tap_reset(jc);
+    bscan_shift_dr(jc, NULL, junk, 32);
+
+    return svf_play_file(&bscan_svf_ops, jc, path, log, user, stats);
+}