feat(recorder): the WASAPI capture sidecar

Cargo.toml

@@ -6,6 +6,9 @@ members = ["crates/recorder"]
 resolver = "2"
 
 [workspace.lints.rust]
-# WASAPI capture needs unsafe; until then, deny it so the skeleton cannot
-# quietly grow an unsafe block that group 4 did not decide to add.
+# Still denied, and group 4 did not need to lift it. WASAPI does need unsafe,
+# but the `wasapi` crate holds it: the recorder drives a safe wrapper rather
+# than hand-written FFI, so the blast radius of a mistake here is a wrong
+# argument rather than undefined behaviour. Keeping the deny means an unsafe
+# block cannot appear without someone deciding to change this line.
 unsafe_code = "deny"

crates/recorder/Cargo.toml

@@ -4,9 +4,28 @@ version = "0.0.0"
 edition = "2021"
 publish = false
 
+# A library plus a thin binary: everything the session does is testable without
+# a process, and `main.rs` is left with the two things a test cannot have — real
+# stdin and a real exit code.
+[lib]
+name = "recorder"
+path = "src/lib.rs"
+
 [[bin]]
 name = "recorder"
 path = "src/main.rs"
 
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+hound = "3.5"
+
+# WASAPI is Windows-only, and so is this dependency. Everything above it — the
+# session, the time map, the track writer, the JSON-RPC — is platform-neutral
+# and tested everywhere, which is what keeps the capture layer a thin edge
+# rather than the part correctness rests on.
+[target.'cfg(windows)'.dependencies]
+wasapi = "0.23"
+
 [lints]
-workspace = true
+workspace = true