test(themes): add git file-status + fake-LSP scenes; theme-keyed overlays

Broaden the before/after gallery's real-UI coverage and make the
overlay-driven scenes theme-faithful:

- New scenes spin up their own harness with the same theme: a git file-status
  explorer (real git repo + git_explorer plugin → file_status_* colors) and an
  LSP status indicator (fake LSP server → status_lsp_on_*). Both are
  best-effort and bounded, so they never hang or misalign frames.
- Add completion-popup and reference/semantic-highlight scenes, and convert the
  diagnostics and diff-highlight overlays to OverlayFace::Style with theme keys
  so diagnostic.*/diff_* render from the theme rather than fixed RGB.
- Replace the unbounded wait_until calls in the best-effort scenes with a
  bounded poll helper (a hung feature can no longer wedge the suite), and swap
  the terminal scene's fixed 500ms sleep for a short bounded poll.
- CI: time-box the render step (`timeout 900`) and the job (timeout-minutes),
  so a hang fails fast instead of running to the runner limit.

A single changed theme renders in ~15-20s (before + after); the run scales
with the number of changed themes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cj5c8LTx6qGzHrHD8v2qGd

Author: claude

.github/workflows/theme-screenshots.yml

@@ -24,6 +24,10 @@ jobs:
   theme-diff:
     name: theme diff gallery
     runs-on: ubuntu-latest
+    # Each changed theme renders ~15-20s (before + after); a job-level cap keeps
+    # a stuck render from wedging the runner. The render step also wraps cargo
+    # in `timeout` for a tighter, clearer failure.
+    timeout-minutes: 20
     steps:
       - name: Checkout (full history for base diff)
         uses: actions/checkout@v6
@@ -49,7 +53,9 @@ jobs:
           FRESH_THEME_BASE_REF: origin/${{ github.base_ref }}
         run: |
           set -o pipefail
-          cargo nextest run \
+          # Hard wall-clock cap so a hung render fails fast instead of running
+          # to the job timeout. Generous enough for a many-theme PR.
+          timeout 900 cargo nextest run \
             --package fresh-editor \
             --test e2e_tests \
             -E 'test(theme_diff_gallery)' \