Reshape SyncStatusStore into a thin probe-and-emit store

docs/SYNC_STATUS_DIRECTORIES.md

@@ -79,11 +79,13 @@ Two pieces replace the fat global:
      directories cannot cheaply recompute git statuses, so re-querying per
      directory would multiply the expensive part.
    - Subscribes to `Backend` (`RepoUpdates`/`Synced` → probe active;
-     `SignerChanged` → clear active + in-flight, emit empty so directories
-     clear) and observes `CheckoutsStore` (associations changed → probe
-     active). The `RepoListStore` observation edge disappears: targets now
-     come from directories, and announcement refreshes re-track through the
-     sidebar's own data path.
+     `SignerChanged` → clear active, emit empty so directories clear) and
+     observes `CheckoutsStore` (associations changed → probe active). The
+     `RepoListStore` observation edge disappears: targets now come from
+     directories, and announcement refreshes re-track through the sidebar's
+     own data path.
+   - Probe requests reach the loop over the same flume-channel wake the
+     profile fetch service uses, so `probe` needs only `&self`.
    - Polls `active` every 180s while it is non-empty; no user signed in →
      clear and idle, same as today.
 2. `SyncStatusDirectory` (per surface entity): the statuses one surface
@@ -121,7 +123,7 @@ mechanism the profile directories rely on, and it composes with
 ```rust
 // signed_state/src/sync_status.rs
 
-/// Fresh statuses for these repositories; empty on signer change.
+/// Statuses for these repositories may have changed; empty on signer change.
 #[derive(Debug, Clone)]
 pub enum SyncEvent {
     Updated(Vec<(RepoAddr, Vec<CheckoutSyncStatus>)>),
@@ -132,8 +134,9 @@ impl EventEmitter<SyncEvent> for SyncStatusStore {}
 /// Thin global: probes tracked repos and broadcasts results. Holds no data.
 pub struct SyncStatusStore {
     active: RefCell<HashSet<RepoAddr>>,
-    in_flight: RefCell<bool>,
-    pass_pending: RefCell<bool>,
+    sender: Sender<()>,
+    in_flight: bool,
+    pass_pending: bool,
     poll_pending: bool,
     tasks: Vec<Task<()>>,
     _subscriptions: Vec<Subscription>,
@@ -198,12 +201,13 @@ these two views.
 ## Migration steps
 
 1. `signed_state`: reshape `sync_status.rs` — add `SyncEvent` +
-   `EventEmitter`, move the probe computation into a service method that
-   emits results, and strip the store of `statuses`, `statuses_of`,
-   `unsynced`, and `RefreshGate` (still used by `RepoListStore` and
-   `CheckoutsStore`, so `refresh.rs` stays). The `Backend` subscription and
-   the 180s poll move to the service; the `RepoListStore` observation is
-   dropped.
+   `EventEmitter`, move the probe computation into a pass that emits results,
+   and strip the store of `statuses`, `statuses_of`, `unsynced`, and
+   `RefreshGate` (still used by `RepoListStore` and `CheckoutsStore`, so
+   `refresh.rs` stays). The `Backend` subscription and the 180s poll move to
+   the service; the `RepoListStore` observation is dropped. `RepoStore::run_push`
+   replaces its post-push `refresh(cx)` with `probe(addr)` so badges update
+   without waiting for the relay pump.
 2. `signed_state`: add `SyncStatusDirectory` in the same file and export it
    from `lib.rs`. `init` keeps creating the global store.
 3. `workspace`: rewire `SidebarPanel` (directory + `track` in `refresh`,
@@ -221,8 +225,11 @@ these two views.
 - **Checkout association added mid-pass**: `CheckoutsStore` observation
   schedules a follow-up pass, so the new path is picked up promptly, not on
   the next 180s tick.
-- **Signer change mid-pass**: directories clear on the empty `Updated` event;
-  a late result for an untracked addr is dropped by `apply`.
+- **Signer change mid-pass**: the in-flight pass is left alone so its
+  completion releases the slot exactly once; its stale results are dropped by
+  directories because the addrs are no longer tracked. The empty `Updated`
+  event clears directories; a later probe re-runs over the new signer's
+  addrs.
 - **No published state for a repo**: the pass skips it (`states.get` miss),
   statuses stay empty, and the pending set is released like today's
   missing-entry behavior.