Add graphical queue (ui.py), fix runaway-clip padding

ui.py — graphical front-end
  Queue several videos and run them one after another. Each job shells out to
  lektor_ai_comfy.py with ordinary command-line arguments, so the terminal
  script stays the single source of truth and remains usable on its own.

  Videos chosen together in one multi-select form a linked set whose settings
  move together; blocks added with + stay independent. Subtitles are found
  beside the video automatically, picked manually, or chosen from the video's
  embedded tracks. REGENERATE / RESUME / RE-BUILD map to --regen,
  --resume-from and --rebuild; RESUME pre-fills the last clip on disk, since an
  interrupted run can leave that one half-written. A Settings dialog edits
  settings.ini in place, rewriting only the value lines so the file's comments
  survive — configparser would have dropped all 29 of them. Closing asks first,
  and names the queued jobs that would be discarded.

  tkinter, so no new dependencies. It needs a Tk with real fonts: the system
  one after `apt install python3-tk`. Under miniforge's Python it still runs but
  falls back to X11 bitmap fonts, which the UI detects and reports.

  Reading the child's pipe deliberately avoids text=True. Text mode enables
  universal newlines, which rewrites a lone carriage return as a newline — so
  ffmpeg's progress bars redrew as a new line per update instead of animating.
  Wheel events are bound per widget rather than with bind_all, so scrolling
  stops at a widget's limit instead of spilling into whatever is behind it, and
  can no longer change a dropdown's value in passing.

start_lektor_ui.sh
  Picks a Python that has tkinter, preferring the system one for its fonts.

Runaway clip padding
  When the model fails to emit a stop token it generates until --max-tokens is
  exhausted: a two-second line becomes a 136s clip. Placement uses a
  push-forward cursor, so that padding delayed every clip after it — measured
  on one film, 1807 of 2075 clips were pushed late, the worst by 981 seconds,
  which is why the voiceover fell silent over later dialogue.

  Clips are now trimmed before they are saved. Two padding modes occur and both
  are handled: digital silence, found with silencedetect; and a steady tone that
  sits above any sane silence threshold, found by its flatness instead — tone
  tails spread 3-5 dB across their windows where speech spreads 43-61 dB.

  --trim-silence repairs jobs generated before this, in place and without
  regenerating anything. Applied to the six existing jobs it removed 77 clips'
  worth of padding, about 1h55m, leaving every job within a few seconds of its
  subtitle timing.

--embedded-sub-index
  Selects an embedded subtitle track by ffmpeg stream index instead of
  prompting, for the UI and for scripted runs. Interactive behaviour is
  unchanged when it is omitted.

settings.ini — voice gudowski_short_3, temperature 0.6.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

start_lektor_ui.sh

@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+#
+# start_lektor_ui.sh — launch the lektor_ai voiceover queue UI.
+#
+# Picks a Python that actually has tkinter. The system one is preferred: its Tk
+# is built against fontconfig and renders real fonts, while the miniforge build
+# only carries legacy X11 bitmap fonts and looks dated. Either will run.
+#
+# ComfyUI needs to be running for GENERATE to do anything — start_comfyui.sh.
+#
+set -euo pipefail
+
+cd "$(dirname "$(readlink -f "$0")")"
+
+if [[ ! -f ui.py ]]; then
+    echo "ui.py not found next to this script ($PWD)" >&2
+    exit 1
+fi
+
+# Preference order, best-looking first.
+CANDIDATES=(
+    /usr/bin/python3
+    python3
+    "$HOME/miniforge3/bin/python"
+    "$HOME/miniforge3/envs/comfy-tts/bin/python"
+)
+
+PY=""
+for c in "${CANDIDATES[@]}"; do
+    if command -v "$c" >/dev/null 2>&1 && "$c" -c "import tkinter" >/dev/null 2>&1; then
+        PY="$c"
+        break
+    fi
+done
+
+if [[ -z "$PY" ]]; then
+    cat >&2 <<'EOF'
+No Python with tkinter was found.
+
+Install it for the system Python (recommended — gives proper fonts):
+    sudo apt install python3-tk
+
+Miniforge's Python also ships tkinter if you have it:
+    ~/miniforge3/bin/python ui.py
+EOF
+    exit 1
+fi
+
+exec "$PY" ui.py "$@"