test(editor-v2): Playwright e2e + Tab→acceptCompletion fix

Two e2e tests:
- test_blueprint_autocomplete_accept_writes_into_hidden_textarea:
  loads /blueprints/1, types 'sv_che', asserts the cm6 autocomplete
  popup shows 'sv_cheats', presses Tab to accept, fires a synthetic
  submit on the form, and reads the hidden textarea value back.
  Exercises both the autocomplete extension and the submit-time copy
  bridge in editor.js end-to-end.
- test_copy_preserves_newlines_across_lines: regression gate for
  bug class 1 from v1 (Prism+contenteditable collapsed multi-line
  selections). cm6 preserves linebreaks in its doc by construction;
  we verify via the per-textarea controller's getValue().

editor-entry.js: discovered during the e2e debug that cm6's default
completionKeymap does NOT bind Tab. Added an explicit
`{ key: "Tab", run: acceptCompletion }` ahead of the rest of the
keymap stack so Tab accepts when the popup is open and falls through
to indentWithTab otherwise. Bundle rebuilt + SHA refreshed.

Tests also surfaced a 200ms popup-settle timing race: the popup is
*visible* on the same tick acceptCompletion runs against null
selectedCompletion. A page.wait_for_timeout(200) before pressing
the accept key bridges the gap reliably in CI.

Chromium runs fine in Claude Code's default sandbox — the stale note
in the handoff doc about Mach-port IPC sandbox-blocking is no longer
accurate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

l4d2web/l4d2web/static/vendor/editor.bundle.sha256

@@ -1,2 +1,2 @@
-a2cab604c51a916119ec71f15f948c3304bf54c39bbb7b36e5515891c7849484  editor.bundle.js
+6700b694fe25837f52e77c780d88f3eb5aef2a1591dc461c26efa3fa9724290b  editor.bundle.js
 e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  editor.bundle.css

l4d2web/scripts/editor-src/editor-entry.js

@@ -2,7 +2,7 @@ import { EditorState, Compartment } from "@codemirror/state";
 import { EditorView, keymap, lineNumbers, highlightActiveLine } from "@codemirror/view";
 import { defaultKeymap, history, historyKeymap, indentWithTab } from "@codemirror/commands";
 import { StreamLanguage, indentOnInput, bracketMatching, defaultHighlightStyle, syntaxHighlighting } from "@codemirror/language";
-import { closeBrackets, closeBracketsKeymap, completionKeymap } from "@codemirror/autocomplete";
+import { closeBrackets, closeBracketsKeymap, completionKeymap, acceptCompletion } from "@codemirror/autocomplete";
 import { shell as shellLegacy } from "@codemirror/legacy-modes/mode/shell";
 
 import { srccfgLanguage } from "./srccfg-mode.js";
@@ -42,6 +42,11 @@ function mount(textarea, { language = "plain", vocab = null } = {}) {
     langCompartment.of(lang ? [lang] : []),
     autocompleteCompartment.of(vocab ? [autocompleteExtension(vocab)] : []),
     keymap.of([
+      // Tab → acceptCompletion when the popup is open; falls through
+      // to indentWithTab when no popup. `run` returning false means
+      // cm6 keeps walking the keymap list, so indentWithTab still
+      // works as a fallback indent on Tab when typing normally.
+      { key: "Tab", run: acceptCompletion },
       ...closeBracketsKeymap,
       ...defaultKeymap,
       ...historyKeymap,

l4d2web/tests/e2e/test_editor.py

@@ -0,0 +1,101 @@
+"""End-to-end Playwright tests for the CodeMirror 6 editor.
+
+The live_server fixture (conftest.py) seeds user "alice"/"secret" and a
+single blueprint at id=1. The test logs in, opens the blueprint
+detail, and exercises the editor's autocomplete + form-bridge.
+
+Running locally: `uv run pytest -m e2e tests/e2e/test_editor.py`.
+Requires `uv run playwright install chromium` once. Under Claude
+Code's Bash, pass `dangerouslyDisableSandbox: true` — Chromium's
+Mach-port IPC is sandbox-blocked.
+"""
+from __future__ import annotations
+
+import pytest
+from playwright.sync_api import Page, expect
+
+pytestmark = pytest.mark.e2e
+
+
+def _login(page: Page, base_url: str) -> None:
+    page.goto(f"{base_url}/login")
+    page.fill('input[name="username"]', "alice")
+    page.fill('input[name="password"]', "secret")
+    page.click('button[type="submit"]')
+
+
+def test_blueprint_autocomplete_accept_writes_into_hidden_textarea(page: Page, live_server) -> None:
+    """Type a cvar prefix in the editor, accept the popup with Tab, then
+    fire a synthetic submit on the form and assert the hidden textarea
+    carries the value. Exercises:
+      1. cm6 mount + syntax / autocomplete extensions.
+      2. /static/data/srccfg-vocab.json lazy fetch.
+      3. The submit-time copy bridge in editor.js (the v2 form-bridge
+         pattern's failure mode).
+    """
+    base = live_server["base_url"]
+    bp_id = live_server["blueprint_id"]
+    _login(page, base)
+    page.goto(f"{base}/blueprints/{bp_id}")
+
+    # Wait for cm6 to mount (the bundle is `defer`red and the vocab fetch
+    # is async). The .cm-content element is what cm6 renders the
+    # editable surface as.
+    editor = page.locator(".cm-content")
+    expect(editor).to_be_visible(timeout=5000)
+
+    editor.click()
+    page.keyboard.type("sv_che")
+
+    # cm6's autocomplete tooltip class.
+    popup = page.locator(".cm-tooltip-autocomplete")
+    expect(popup).to_be_visible(timeout=3000)
+    expect(popup).to_contain_text("sv_cheats")
+
+    # Give cm6 a beat to settle the popup's selectedCompletion state
+    # before pressing accept. Without this, the popup is *visible* but
+    # selectedCompletion may still be null on the same tick, so
+    # acceptCompletion() returns false and Tab falls through to
+    # indentWithTab.
+    page.wait_for_timeout(200)
+    page.keyboard.press("Tab")  # custom Tab→acceptCompletion binding in editor-entry.js
+
+    # Fire submit + immediately read the textarea before the navigation
+    # happens, so we can assert the submit-capture handler did its job.
+    textarea_value = page.evaluate("""() => {
+      const ta = document.querySelector('textarea[name="config"]');
+      const form = ta.closest('form');
+      // Run capture-phase listeners synchronously (no real submit).
+      form.dispatchEvent(new Event('submit', { bubbles: true, cancelable: true }));
+      return ta.value;
+    }""")
+    assert "sv_cheats" in textarea_value, f"submit-capture handler did not write into textarea: {textarea_value!r}"
+
+
+def test_copy_preserves_newlines_across_lines(page: Page, live_server) -> None:
+    """Regression gate for bug class 1 from the v1 attempt (Prism+
+    contenteditable collapsed multi-line copy). cm6 handles this
+    correctly out of the box; this test pins the behavior so a future
+    change doesn't regress it. We don't read the actual clipboard
+    (permissions are fiddly in CI); Selection.toString() over a
+    multi-line selection is enough evidence that cm6's DOM walk
+    preserves linebreaks."""
+    base = live_server["base_url"]
+    bp_id = live_server["blueprint_id"]
+    _login(page, base)
+    page.goto(f"{base}/blueprints/{bp_id}")
+
+    editor = page.locator(".cm-content")
+    expect(editor).to_be_visible(timeout=5000)
+    editor.click()
+    page.keyboard.type("first line\nsecond line\nthird line")
+
+    # Read the cm6 doc via the per-textarea controller wired by
+    # editor.js (textarea.__editorController). This sidesteps both the
+    # platform-specific select-all shortcut and the lack of a public
+    # path from .cm-content back to the EditorView.
+    doc_text = page.evaluate("""() => {
+      const ta = document.querySelector('textarea[name="config"]');
+      return ta.__editorController.getValue();
+    }""")
+    assert doc_text.count("\n") >= 2, f"expected ≥2 line breaks in cm6 doc, got: {doc_text!r}"