fix(site/src/pages/AgentsPage): dismiss skills trigger on outside click (#25613)

When the personal skills menu is open and the user clicks outside (e.g.
the send button), the Popover closes via `onOpenChange` but the
`SkillsTriggerPlugin`'s `dismissedTriggerRef` is not set. The next
Lexical update listener call detects the trigger again and briefly
reopens the menu, causing a visible flash.

Addresses this symptom:


https://github.com/user-attachments/assets/0c1442a2-df75-442b-bcf8-4b028dc647b0



Fix by recording the current trigger position in `dismissedTriggerRef`
when the `open` prop transitions from `true` to `false`. This mirrors
what the Escape key handler already does and prevents `refreshTrigger`
from immediately re-opening the menu at the same position.

<details><summary>Implementation details</summary>

- Added a `useLayoutEffect` in `SkillsTriggerPlugin` that tracks `open`
prop transitions via a `prevOpenRef`. When `open` goes from `true` to
`false`, it snapshots the current trigger position into
`dismissedTriggerRef`, matching the pattern the Escape handler uses
(line 225-227).
- Added `OutsideClickDismissesTriggerOnRefocus` Storybook regression
story that verifies the menu stays closed when clicking back into the
editor after an outside-click dismissal.

</details>

---

*PR generated with Coder Agents*

site/src/pages/AgentsPage/components/ChatMessageInput/ChatMessageInput.stories.tsx

@@ -219,3 +219,18 @@ export const OutsideClickClosesWithoutReplacing: Story = {
 		expect(editor.textContent).toBe("/");
 	},
 };
+
+export const OutsideClickDismissesTriggerOnRefocus: Story = {
+	play: async ({ canvasElement }) => {
+		const editor = await typeInEditor(canvasElement, "/");
+		await findVisibleText("/reviewer");
+		const canvas = within(canvasElement);
+		await userEvent.click(
+			canvas.getByRole("button", { name: "Outside target" }),
+		);
+		await expectNoVisibleText("/reviewer");
+		await userEvent.click(editor);
+		await expectNoVisibleText("/reviewer");
+		expect(editor.textContent).toBe("/");
+	},
+};

site/src/pages/AgentsPage/components/ChatMessageInput/SkillsTriggerPlugin.tsx

@@ -11,7 +11,7 @@ import {
 	KEY_TAB_COMMAND,
 	type NodeKey,
 } from "lexical";
-import { useEffect, useEffectEvent, useRef } from "react";
+import { useEffect, useEffectEvent, useLayoutEffect, useRef } from "react";
 import type * as TypesGen from "#/api/typesGenerated";
 import { parsePersonalSkillTrigger } from "../../utils/personalSkills";
 import type { CaretAnchorRect } from "./PersonalSkillsTriggerMenu";
@@ -121,6 +121,16 @@ export const SkillsTriggerPlugin = ({
 	const [editor] = useLexicalComposerContext();
 	const dismissedTriggerRef = useRef<DismissedSkillsTrigger | null>(null);
 
+	const prevOpenRef = useRef(open);
+	useLayoutEffect(() => {
+		if (prevOpenRef.current && !open) {
+			dismissedTriggerRef.current = editor
+				.getEditorState()
+				.read(() => activeTriggerFromSelection());
+		}
+		prevOpenRef.current = open;
+	}, [open, editor]);
+
 	const refreshTrigger = useEffectEvent(() => {
 		const trigger = editor.getEditorState().read(() => {
 			return editor.isEditable() ? activeTriggerFromSelection() : null;