feat: add OBS recording engine and validation probe

clipbin-obs starts the pinned libobs on a dedicated thread, opens exactly the
bundled plugin allowlist, and records official capture sources through one
hardware encoder into keyframe-aligned Matroska segments. Status reaches
Recording only once the source has a picture and the segment grows on disk.

clipbin-probe lists and verifies hardware encoders and records from a real
capture source, printing status, health and segment events for validation.

Cargo.toml

@@ -1,5 +1,10 @@
 [workspace]
-members = ["crates/clipbin-core", "crates/clipbin-desktop"]
+members = [
+    "crates/clipbin-core",
+    "crates/clipbin-desktop",
+    "crates/clipbin-obs",
+    "crates/clipbin-probe",
+]
 default-members = ["crates/clipbin-desktop"]
 resolver = "3"
 
@@ -13,7 +18,11 @@ publish = false
 
 [workspace.dependencies]
 clipbin-core = { path = "crates/clipbin-core" }
+clipbin-obs = { path = "crates/clipbin-obs" }
 gpui = "=0.2.2"
+# The tested OBS set: the libobs crate's bundled headers are OBS 32.0.4, matching
+# scripts/obs/versions.env. Update them together.
+libobs = "=5.0.1"
 
 [workspace.lints.rust]
 unsafe_code = "forbid"