M0 scaffold — Python addon + Rust sidecar

Kodi addon (plugin.video.torttube) shell with Cargo workspace for the
rustypipe-backed sidecar binary. No working extraction yet — addon.xml
parses, main.py is a notification stub, sidecar's main.rs prints scaffold
banner. See MILESTONES.md for M1..M6.

License: GPL-3.0-or-later (matches rustypipe + NewPipeExtractor).

sidecar/crates/torttube-sidecar/src/main.rs

@@ -0,0 +1,9 @@
+// torttube-sidecar — JSON-over-stdio bridge between Kodi (Python) and YouTube extraction.
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+// Reads one JSON request per line from stdin, writes one JSON response per line to stdout.
+// M0 scaffold — handlers land in M1+ (resolve, sponsorblock, search, channel, playlist).
+
+fn main() {
+    eprintln!("torttube-sidecar M0 scaffold — see MILESTONES.md");
+}