Merge master into the face branch

Master moved 24 commits while this branch was building the face sweep, and one
of them changed how the interface reaches a server: `remote.rs` is now the only
file that names a connector, and everything else takes `&dyn RemoteBackend`.
The face sweep was written before that landed and built a `NextcloudBackend`
directly. Git merged the text without complaint and the result did not compile,
which is the useful kind of conflict — it goes through `remote::connect` now,
like every other pass.

Two documentation conflicts, both resolved toward master. `code-health.md` was
an add/add: master's copy carries the CH resolution for the backend seam and a
better provenance note, so it wins outright, with its measured figures re-taken
against the merged tree rather than either side's — `run()` is 1,855 lines now,
2,042 tests, 793 traceability tags. `traceability.md` is generated, so it was
regenerated rather than hand-merged.

The seam grades in code-health.md are unchanged by this merge. That is worth
noticing rather than glossing: the face work went into the seams that already
existed — `run()`, `library.rs`, `AppWindow` — which is exactly the pressure
CH-1 describes rather than evidence against it.

All four CI jobs pass: desktop (fmt, clippy, test, build), layering, traceability,
and the Android cross-build.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/dr-ui/src/library.rs

@@ -2904,7 +2904,9 @@ pub fn spawn_face_sweep(
         };
 
         rt.block_on(async {
-            let backend = match NextcloudBackend::new(&creds, &user_id) {
+            // Through `remote::connect`, which is the only place in the
+            // interface that knows whose backend this is.
+            let backend = match crate::remote::connect(&creds, &user_id) {
                 Ok(b) => b,
                 Err(e) => {
                     log::warn!("face sweep: {e}");
@@ -2931,7 +2933,7 @@ pub fn spawn_face_sweep(
                     .collect();
 
                 let results = futures_join_all(lanes.into_iter().map(|lane| {
-                    let backend = &backend;
+                    let backend = &*backend;
                     let models = ⊧
                     let options = &options;
                     async move {