scaffold the Godot port, as its own repo with its own agent

The port is deliberately separate from the reverse-engineering project: its own
repository, its own clone, its own container. Two writers in one working tree
means files change under whoever is mid-edit and a `git add -A` by one sweeps up
the other's work -- which happened today in the Reborn tree, so this is set up
not to repeat it.

The wall: Godot never reads a disc format. An offline Rust exporter converts the
user's disc into JSON + PNG + Ogg, and the Godot project reads only that. No
GDExtension, no Rust in port/. Beyond the practical reason -- Godot cannot read
IPFB, RATC, T8aD, XMA or WMV -- there is the design one: modding is a goal, and
if the runtime reads the original formats then modding means reverse
engineering, whereas if it reads JSON it means opening a file.

The decoders come from sylpheed-formats PINNED BY REVISION (8b6dbcf), not
vendored and not reimplemented. `sylpheed_formats::media` in particular already
owns every case where one playable thing is not one archive entry: entries that
span segment files, banks with several sub-waves, and the cutscene voices, which
are one continuous XMA stream chunked into VOICE_*.slb entries whose boundaries
do NOT match the cues. That last one is the easiest thing in this project to get
subtly wrong, so the mission says outright not to re-derive it.

docs/MISSION.md is the objective (P0-P7, each gated by an artifact rather than
by compiling). docs/BLOCKED.md lists what cannot proceed until the RE agent
answers Q1-Q10, and says plainly that none of it may be guessed -- this agent
has no emulator and no oracle, so a value it invents is indistinguishable from a
decoded one a month later.

The container is deliberately small: 3 cpus / 4 GB against the RE container's
6 / 7, and an image with no C++ toolchain, no Vulkan stack and no emulator. Two
full-size containers do not fit on this box beside a desktop.

Its launcher sets the git identity through GIT_AUTHOR_*/GIT_COMMITTER_* rather
than writing [user] into .git/config -- the config route captures every commit
made in that tree, including a human's, which is how six of today's commits
ended up attributed to the RE agent.

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

crates/sylpheed-export/src/main.rs

@@ -0,0 +1,33 @@
+//! Convert a Project Sylpheed disc into the open asset tree the Godot port reads.
+//!
+//! The one rule this binary exists to enforce: **Godot never sees a disc format.**
+//! Everything proprietary is decoded here and written out as JSON, PNG, Ogg
+//! Vorbis and Ogg Theora, so the runtime — and anyone modding it — reads formats
+//! a person can open.
+//!
+//! See `docs/FORMAT.md` for the schema and `docs/MISSION.md` for scope.
+
+use anyhow::Result;
+use clap::Parser;
+use std::path::PathBuf;
+
+#[derive(Parser)]
+#[command(about, version)]
+struct Args {
+    /// Extracted disc root (the directory holding `dat/` and `hidden/`).
+    #[arg(long)]
+    disc: PathBuf,
+    /// Output tree. Rewritten wholesale — never hand-edit it.
+    #[arg(long, default_value = "export")]
+    out: PathBuf,
+}
+
+fn main() -> Result<()> {
+    let args = Args::parse();
+    let source = sylpheed_formats::media::DirectorySource::new(&args.disc);
+    // P0 starts here: enumerate GP_TITLE's screen builds and write one out.
+    // Nothing is implemented yet -- this proves the pinned decoders resolve.
+    let _ = (&source, &args.out);
+    println!("sylpheed-export: scaffold only; see docs/MISSION.md milestone P0");
+    Ok(())
+}