Regenerate episode pages and sitemap during publish

add_episode_to_sitemap() was removed in the previous commit, so nothing was
writing the sitemap any more. Publishing now shells out to
generate_episode_pages.py --sitemap right after the transcript is copied into
website/transcripts/, which builds the new episode's static page and rebuilds
the sitemap from the feed.

Deliberately non-fatal: by this point the audio is live on Castopod and the RSS
feed has been rebuilt, so a generator failure must not abort the publish. It
warns and moves on, and the page lands on the next run. Covered for non-zero
exit, timeout, and a missing generator script.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_publish_regenerates_pages.py

@@ -0,0 +1,80 @@
+"""Publishing must rebuild the static episode pages and the sitemap.
+
+Before static pages existed, publish_episode.py appended one entry to
+sitemap.xml itself. That appender is gone — generate_episode_pages.py owns the
+sitemap now — so the publish has to invoke it, or a newly published episode
+would have no page and never reach the sitemap.
+
+A generator failure must never abort a publish: by the time this runs the audio
+is already live on Castopod and the RSS feed has been rebuilt.
+"""
+
+import subprocess
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+import publish_episode
+
+
+class _Result:
+    def __init__(self, returncode=0, stderr=""):
+        self.returncode = returncode
+        self.stderr = stderr
+        self.stdout = ""
+
+
+def test_invokes_the_generator_with_sitemap(monkeypatch):
+    calls = []
+    monkeypatch.setattr(subprocess, "run", lambda cmd, **kw: calls.append(cmd) or _Result())
+
+    assert publish_episode.regenerate_website_pages() is True
+
+    assert len(calls) == 1
+    cmd = calls[0]
+    assert "generate_episode_pages.py" in " ".join(cmd)
+    assert "--sitemap" in cmd
+
+
+def test_uses_the_running_interpreter(monkeypatch):
+    """Must not shell out to a bare 'python' that may not have the venv."""
+    calls = []
+    monkeypatch.setattr(subprocess, "run", lambda cmd, **kw: calls.append(cmd) or _Result())
+
+    publish_episode.regenerate_website_pages()
+
+    assert calls[0][0] == sys.executable
+
+
+def test_generator_failure_is_not_fatal(monkeypatch):
+    monkeypatch.setattr(subprocess, "run",
+                        lambda cmd, **kw: _Result(returncode=1, stderr="boom"))
+
+    assert publish_episode.regenerate_website_pages() is False
+
+
+def test_generator_timeout_is_not_fatal(monkeypatch):
+    def _boom(cmd, **kw):
+        raise subprocess.TimeoutExpired(cmd, 300)
+
+    monkeypatch.setattr(subprocess, "run", _boom)
+
+    assert publish_episode.regenerate_website_pages() is False
+
+
+def test_missing_generator_is_not_fatal(monkeypatch):
+    def _boom(cmd, **kw):
+        raise OSError("no such file")
+
+    monkeypatch.setattr(subprocess, "run", _boom)
+
+    assert publish_episode.regenerate_website_pages() is False
+
+
+def test_publish_flow_calls_it_after_copying_the_transcript():
+    """Guards the wiring, not just the helper."""
+    source = Path(publish_episode.__file__).read_text()
+    copy_at = source.index("Transcript copied to website/transcripts/")
+    call_at = source.index("regenerate_website_pages()", copy_at)
+    assert call_at > copy_at