Add configurable group session scope (default user_in_chat).

Ops bots now isolate per-speaker Harness sessions in groups, with a
settings/RPC toggle to restore shared chat sessions when needed.

Co-authored-by: Cursor <cursoragent@cursor.com>

test/channels/shared/session-scope.test.mjs

@@ -0,0 +1,61 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+
+import {
+  conversationKeyFor,
+  DEFAULT_GROUP_SESSION_SCOPE,
+  normalizeGroupSessionScope,
+  validateGroupSessionScope,
+} from '../../../src/channels/shared/session-scope.mjs';
+
+describe('session-scope', () => {
+  it('defaults ops fork to user_in_chat', () => {
+    assert.equal(DEFAULT_GROUP_SESSION_SCOPE, 'user_in_chat');
+    assert.equal(normalizeGroupSessionScope(undefined), 'user_in_chat');
+    assert.equal(normalizeGroupSessionScope('shared'), 'chat');
+    assert.equal(normalizeGroupSessionScope('per_user'), 'user_in_chat');
+  });
+
+  it('validates strict scopes only', () => {
+    assert.equal(validateGroupSessionScope('chat'), 'chat');
+    assert.equal(validateGroupSessionScope('user_in_chat'), 'user_in_chat');
+    assert.throws(() => validateGroupSessionScope('shared'), /Invalid group session scope/);
+  });
+
+  it('builds direct and group conversation keys', () => {
+    assert.equal(
+      conversationKeyFor({ kind: 'direct', conversationId: 'u1', senderId: 'u1' }),
+      'direct:u1',
+    );
+    assert.equal(
+      conversationKeyFor({
+        kind: 'group',
+        conversationId: 'g1',
+        senderId: 'u2',
+        groupSessionScope: 'chat',
+      }),
+      'group:g1',
+    );
+    assert.equal(
+      conversationKeyFor({
+        kind: 'group',
+        conversationId: 'g1',
+        senderId: 'u2',
+        groupSessionScope: 'user_in_chat',
+      }),
+      'group:g1:user:u2',
+    );
+  });
+
+  it('requires senderId for user_in_chat groups', () => {
+    assert.throws(
+      () => conversationKeyFor({
+        kind: 'group',
+        conversationId: 'g1',
+        senderId: '',
+        groupSessionScope: 'user_in_chat',
+      }),
+      /senderId is required/,
+    );
+  });
+});