chore: start transition layout — python into version-python/, scaffold version-rust/

- git mv of all existing files into version-python/ (history preserved)
- version-rust/: minimal cargo scaffold (edition 2024), no deps yet
- root AGENTS.md documents the transition rules and artifact/schema contract
- main is untouched; the python layout there stays as-is

version-python/parts/grab.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+THREAD_ID="${THREAD_ID:-1455993943471820842}"
+OUT_DIR="${OUT_DIR:-$PWD/thread}"
+HTML="$OUT_DIR/export.html"
+URLS="$OUT_DIR/urls.txt"   # aria2c input file: one URL per line
+
+# Token from env, otherwise prompt (input hidden)
+if [[ -z "${DISCORD_TOKEN:-}" ]]; then
+  read -rsp "Discord token: " DISCORD_TOKEN
+  echo
+fi
+
+mkdir -p "$OUT_DIR"
+
+# 1. Export the thread to HTML
+docker run --rm --user "$(id -u):$(id -g)" \
+  -v "$OUT_DIR:/out" \
+  tyrrrz/discordchatexporter:stable export \
+  -t "$DISCORD_TOKEN" -c "$THREAD_ID" -f HtmlDark -o /out/export.html
+
+unset DISCORD_TOKEN
+
+# 2. Find base64 strings starting with "https://", then decode them
+grep -oP 'aHR0cHM6Ly[89][A-Za-z0-9+/_-]*' "$HTML" \
+  | sort -u \
+  | while read -r s; do
+      s=$(printf '%s' "$s" | tr '_-' '/+' | tr -d '=')
+      while (( ${#s} % 4 )); do s="$s="; done
+      printf '%s' "$s" | base64 -d 2>/dev/null | tr -d '\r\n' || true
+      echo
+    done \
+  | grep -E '^https://[[:graph:]]+$' \
+  | awk '!seen[$0]++' > "$URLS"
+
+echo "Found $(wc -l < "$URLS") URLs -> $URLS"
+echo "Download with: aria2c -i \"$URLS\" -d \"$OUT_DIR/downloads\""