Bluetooth mic startup: honest Listening indicator, startup-time investigation

The bar turned green after 2 s on a timer even when the microphone delivered
nothing. It now turns green only on real audio: RMS above 0.0005, or three
consecutive chunks that are not digital silence (the virtual mic emits one
stray nonzero chunk right after start, and a Bluetooth headset's floor ramps
in from a few LSB). Measured 1.2-1.4 s after the key, within 0.14 s of the
first real samples.

diagnostics/bluetooth/ records how startup went from ~1.6 s (or never) to
~1.1-1.4 s: a btusb driver bug, two PipeWire bluez5 bugs, a 500 ms WirePlumber
switch timeout and an over-broad auto-connect rule. Those fixes are machine
level and live outside this repo; the patches, tools and measurements are here.
STARTUP-TIME.md is the summary and explains the ~0.9 s hardware floor.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Xoc9DJCViR7dg9eKzzAcfQ

diagnostics/bluetooth/tools/trial.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# One dictation startup trial: kernel probes + btmon + userspace timing. $1 = label
+set -u
+SC=$(dirname "$0"); L=${1:-trial}; S=/sys/kernel/tracing
+sudo -n sh -c "echo > $S/trace"
+sudo -n btmon -w "$SC/$L.btsnoop" >/dev/null 2>&1 &
+BTMON=$!
+sleep 0.5
+T0=$(date +%s.%N)
+echo "T0 unix $T0  monotonic $(python3 -c 'import time;print(round(time.monotonic(),3))')"
+python3 /tmp/stt-startup-trace.py 2>&1 | grep -vE '"graph"|audio-progress'
+sleep 0.5
+sudo -n kill $BTMON; wait $BTMON 2>/dev/null
+echo "--- ftrace"
+sudo -n cat $S/trace | grep -v '^#' | grep -vE 'sco_tx|sco_rx_urb' | sed -E 's/^ +//; s/ \[[0-9]+\] [^ ]+ / /; s/\([^)]*\)//' | cut -c1-120
+echo "--- sco tx/rx-urb per second"
+sudo -n cat $S/trace | grep -E 'sco_tx|sco_rx_urb' | sed -E 's/.* ([0-9]+)\.[0-9]+: (sco_tx|sco_rx_urb).*/\1 \2/' | sort | uniq -c | tr '\n' ';'; echo
+echo "--- dmesg"
+sudo -n journalctl -k -o short-precise --since "@${T0%.*}" --no-pager | grep -E 'Bluetooth:|hci_sync_conn|hci_conn_request|btusb_notify|__set_isoc|btusb_submit_isoc|__fill_isoc' | cut -c1-160
+echo "--- btmon (commands/events only)"
+sudo -n chown $USER "$SC/$L.btsnoop"
+btmon -r "$SC/$L.btsnoop" -t 2>/dev/null | grep -E '^[<>] HCI (Command|Event)|^\s+(Status|Handle|Link type|Air mode|Reason|Opcode|Voice setting|Transmit coding|Receive coding|RX packet length|TX packet length|Mode|Interval|Packet type|Retransmission|Max latency|Transmit bandwidth|Receive bandwidth):' | grep -vE 'HCI Event: Number of Completed|HCI Event: Command Complete.*(Read RSSI|Read Clock)|Vendor' | sed -E 's/\{[^}]*\}//' | cut -c1-140