test(e2e): editor autocomplete end-to-end

Logs in as the seed user, navigates to the blueprint detail page,
types sv_che into the editor, asserts the autocomplete popup appears
with sv_cheats, accepts via Tab, and asserts the hidden textarea
(form field) now contains the inserted cvar.

This exercises the full chain end-to-end: editor mount on
DOMContentLoaded, srccfg-vocab.json fetch, popup positioning,
capture-phase keydown handling (Task 9 fix), Range-API completion
insertion, and textarea-mirroring on every input.

l4d2web/tests/e2e/test_editor.py

@@ -0,0 +1,58 @@
+"""End-to-end test for the textarea code editor.
+
+Logs in as the seed user, navigates to the blueprint detail page, types
+`sv_che` into the editor, asserts the autocomplete popup appears with
+`sv_cheats`, accepts via Tab, and asserts the underlying textarea now
+contains `sv_cheats`.
+"""
+
+import pytest
+from playwright.sync_api import expect, sync_playwright
+
+
+@pytest.mark.e2e
+def test_editor_autocomplete_inserts_cvar(live_server) -> None:
+    base = live_server["base_url"]
+    blueprint_id = live_server["blueprint_id"]
+
+    with sync_playwright() as p:
+        browser = p.chromium.launch()
+        ctx = browser.new_context()
+        page = ctx.new_page()
+
+        # Log in.
+        page.goto(f"{base}/login")
+        page.fill('input[name="username"]', "alice")
+        page.fill('input[name="password"]', "secret")
+        page.click('button[type="submit"]')
+        expect(page).to_have_url(f"{base}/dashboard", timeout=5000)
+
+        # Navigate to the seeded blueprint.
+        page.goto(f"{base}/blueprints/{blueprint_id}")
+
+        # Editor mounts on DOMContentLoaded; the contenteditable replaces
+        # the textarea visually. Wait for it.
+        editor = page.locator(".editor-code").first
+        expect(editor).to_be_visible(timeout=5000)
+
+        # Focus the editor and type a cvar prefix.
+        editor.click()
+        page.keyboard.type("sv_che")
+
+        # The popup should appear and contain sv_cheats.
+        popup = page.locator(".editor-popup")
+        expect(popup).to_be_visible(timeout=2000)
+        expect(popup).to_contain_text("sv_cheats")
+
+        # Accept via Tab. Verifies Task 9's capture-phase keydown fix:
+        # CodeJar would otherwise consume Tab and insert 2 spaces
+        # before our popup handler ran.
+        page.keyboard.press("Tab")
+
+        # The hidden textarea (form field) must now contain the cvar.
+        textarea_value = page.evaluate(
+            "() => document.querySelector('textarea[name=config]').value"
+        )
+        assert "sv_cheats" in textarea_value
+
+        browser.close()