Refactor http and websocket implementations into its own crate

.changeset/livekit-net-transport-seam.md

@@ -0,0 +1,19 @@
+---
+livekit-api: major
+livekit: major
+livekit-uniffi: minor
+---
+
+Route LiveKit signalling through a pluggable, host-providable transport (new `livekit-net` crate).
+
+The signalling WebSocket and the two pre-connect HTTP GETs (validate, region discovery) now go through a transport trait resolved from a process-global registry, so mobile/UniFFI builds can drop the Rust TLS/WebSocket/HTTP stack and use the platform's network stack. Native desktop builds are unchanged in behavior.
+
+**Breaking (`livekit-api`, and `livekit` via `EngineError::Signal`):**
+
+- `SignalError::WsError` is removed — `tungstenite` is no longer part of the public API. A failed WebSocket handshake now surfaces its HTTP status as `SignalError::Client`/`Server`; transport connection and close failures surface as the new `SignalError::Connection(String)` / `SignalError::Closed` variants (previously all collapsed into `Timeout`).
+- `SignalError` is now `#[non_exhaustive]`.
+- The signalling WebSocket/HTTP/TLS crates are no longer transitive dependencies of `livekit-api`; TLS features delegate to `livekit-net`. Existing `signal-client-tokio` / `-async` / `-dispatcher` and TLS feature names are unchanged.
+
+`livekit` adds a `foreign` feature that pairs the backend-agnostic signalling client with a host-provided transport.
+
+`livekit-uniffi` gains `setPlatformTransport` so a Dart/Swift/Kotlin host can inject its own transport across the UniFFI boundary, and drops the services (reqwest) stack from the cdylib.

.github/workflows/builds.yml

@@ -154,6 +154,13 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-cargo-target-${{ matrix.target }}-
 
+      # Runtime-invariant: livekit (desktop) is tokio-only; livekit-uniffi uses
+      # the foreign+tokio feature pair, which also resolves to tokio at the
+      # livekit-runtime layer.  Both crates therefore satisfy the one-runtime
+      # guard when built together via --workspace.
+      # IMPORTANT: a future cdylib that uses foreign+dispatcher/async-std MUST
+      # NOT share this --workspace invocation; use its own build job (like the
+      # uniffi-cdylib.yml `-p livekit-uniffi` job) so the runtimes do not clash.
       - name: Build (Cargo)
         if: ${{ !contains(matrix.target, 'android') }}
         run: |

.github/workflows/tests.yml

@@ -162,4 +162,12 @@ jobs:
             --features __lk-e2e-test \
             -- \
             --nocapture \
-            --test-threads=1
+            --test-threads=1
+
+      - name: Test transport seam (livekit-net / signal-client / uniffi)
+        shell: bash
+        run: |
+          cargo test --verbose --target ${{ matrix.target }} -p livekit-net --features native-tokio
+          cargo test --verbose --target ${{ matrix.target }} -p livekit-net --features foreign
+          cargo test --verbose --target ${{ matrix.target }} -p livekit-api --features signal-client-tokio
+          cargo test --verbose --target ${{ matrix.target }} -p livekit-uniffi