fix(desktop): scope thread typing to the thread root, not reply parent

getTypingScopeId keyed typing entries on the reply parent tag, so an agent
working deep in a thread produced a threadHeadId that matched no ingress row
(and missed the open-thread composer filter). Typing and completion events
already carry a root tag for nested replies — prefer it, falling back to the
parent for direct replies where root === parent and no root tag is emitted.

Both the registration and post-message suppression paths flow through the
same helper, so suppression keys stay consistent. Exported for tests.

Co-authored-by: Taylor Ho <taylorkmho@gmail.com>
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>

desktop/src/features/messages/useChannelTyping.test.mjs

@@ -0,0 +1,42 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+
+import { getTypingScopeId } from "./useChannelTyping.ts";
+
+const ROOT = "aaaa".repeat(16);
+const PARENT = "bbbb".repeat(16);
+const CHANNEL = "11111111-1111-1111-1111-111111111111";
+
+describe("getTypingScopeId", () => {
+  it("returns null for channel-scoped typing (no e tags)", () => {
+    assert.equal(getTypingScopeId({ tags: [["h", CHANNEL]] }), null);
+  });
+
+  it("uses the reply parent for direct replies to the thread head", () => {
+    // Direct replies tag only the parent (root === parent, so no root tag).
+    assert.equal(
+      getTypingScopeId({
+        tags: [
+          ["h", CHANNEL],
+          ["e", ROOT, "", "reply"],
+        ],
+      }),
+      ROOT,
+    );
+  });
+
+  it("prefers the thread root over the reply parent for nested replies", () => {
+    // Nested replies tag both root and their immediate parent; thread
+    // surfaces (ingress badge, open-thread composer) key on the root.
+    assert.equal(
+      getTypingScopeId({
+        tags: [
+          ["h", CHANNEL],
+          ["e", ROOT, "", "root"],
+          ["e", PARENT, "", "reply"],
+        ],
+      }),
+      ROOT,
+    );
+  });
+});

desktop/src/features/messages/useChannelTyping.ts

@@ -57,8 +57,15 @@ function isTypingCompletionEvent(event: RelayEvent | null | undefined) {
   );
 }
 
-function getTypingScopeId(event: RelayEvent) {
-  return getThreadReference(event.tags).parentId ?? null;
+/**
+ * Thread scope for a typing/completion event: the thread root, not the
+ * immediate reply parent. Agents replying deep in a thread tag their nested
+ * parent, but every thread surface (ingress badge, open-thread composer)
+ * keys on the thread head id. Exported for tests.
+ */
+export function getTypingScopeId(event: Pick<RelayEvent, "tags">) {
+  const reference = getThreadReference(event.tags);
+  return reference.rootId ?? reference.parentId ?? null;
 }
 
 function getTypingStateKey(pubkey: string, threadHeadId: string | null) {