fix(core): create session if no current and no last

If we're not starting a new session, we don't have a current session and
we don't have a last session, we have to create a new session.

Without a session, submitting prompts fails silently.

Author: cameronr

lua/opencode/core.lua

@@ -76,6 +76,9 @@ function M.open(opts)
   else
     if not state.active_session then
       state.active_session = session.get_last_workspace_session()
+      if not state.active_session then
+        state.active_session = M.create_new_session()
+      end
     else
       if not state.display_route and are_windows_closed then
         -- We're not displaying /help or something like that but we have an active session

tests/unit/core_spec.lua

@@ -170,6 +170,18 @@ describe('opencode.core', function()
       assert.is_false(input_focused)
       assert.is_true(output_focused)
     end)
+
+    it('creates a new session when no active session and no last session exists', function()
+      state.windows = nil
+      state.active_session = nil
+      session.get_last_workspace_session:revert()
+      stub(session, 'get_last_workspace_session').returns(nil)
+
+      core.open({ new_session = false, focus = 'input' })
+
+      assert.truthy(state.active_session)
+      assert.truthy(state.active_session.id)
+    end)
   end)
 
   describe('select_session', function()