fix: decouple oneliner-heal from request handler tasks

heal_orphans_if_idle called regenerate_missing_oneliners_for_user
inline on the request task, blocking the browser for up to N×60s
when orphans existed (observed with 16 cases after manual cleanup).

Now: CAS on new OnelinerHealBusy flag + tokio::spawn + BusyGuard
reset-on-drop. Handler returns immediately; the existing
OnelinerUpdated SSE event delivers results via the usual reload.
Startup recovery shares the flag so a concurrent page-load during
boot cannot fire a parallel regen loop against Ollama.

Regression test uses wiremock + timeout(150ms) + .expect(5) to
verify both non-blocking return and dedup of parallel invocations.

server/src/main.rs

@@ -116,6 +116,12 @@ async fn main() {
     // subscribed browsers.
     let events_tx = events::channel();
 
+    // Dedup flag shared by the startup oneliner-regen task and every
+    // request-driven `heal_orphans_if_idle` spawn. One-at-a-time semantics
+    // keep Ollama from seeing overlapping regen loops.
+    let oneliner_heal_busy: doctate_server::WorkerBusy =
+        std::sync::Arc::new(std::sync::atomic::AtomicBool::new(false));
+
     // Transcription pipeline: channel + worker + recovery scan.
     let (transcribe_tx, transcribe_rx) = transcribe::channel();
     let transcribe_busy: doctate_server::WorkerBusy =
@@ -135,10 +141,14 @@ async fn main() {
         let cfg = config.clone();
         let vocab = vocab.clone();
         let events = events_tx.clone();
+        let heal_busy = oneliner_heal_busy.clone();
         tokio::spawn(async move {
             transcribe::recovery::scan_and_enqueue(&data_path, &tx).await;
             // Then catch up oneliners for cases that crashed between
             // transcript-write and oneliner-write in a previous run.
+            // Hold the shared heal-busy flag while running so a concurrent
+            // page-load does not spawn a second parallel regen loop.
+            let _guard = doctate_server::BusyGuard::new(heal_busy);
             transcribe::recovery::regenerate_missing_oneliners(
                 &data_path, &client, &cfg, &vocab, &events,
             )
@@ -174,6 +184,7 @@ async fn main() {
         magic_link_store: doctate_server::magic_link::new_store(),
         analyze_busy: doctate_server::AnalyzeBusy(analyze_busy),
         transcribe_busy: doctate_server::TranscribeBusy(transcribe_busy),
+        oneliner_heal_busy: doctate_server::OnelinerHealBusy(oneliner_heal_busy),
         events_tx,
         http_client,
         vocab,