Refine dateline format; fix stale page caching breaking theme hot swap

Dateline is now '1 Jan 2026', with ' – edited 3 Jan 2026' appended only
when the last edit came at least 24h after publishing.

The Last-Modified header added heuristic browser caching of pages (no
Cache-Control was sent), so the site editor's re-fetch after a theme
change served the cached page with the old stylesheet link. Pages now
send 'Cache-Control: no-cache' — always revalidate, still cheap via the
ETag.

pagerite/app.py

@@ -668,13 +668,20 @@ async def show_page(request: Request, path: str) -> HTMLResponse | Response:
     node = chain[-1] if chain else None
     if node is not None and node.published and node.content is not None:
         # ETag on content + render version; clients revalidate cheaply,
-        # which keeps prefetched pages warm and current.
+        # which keeps prefetched pages warm and current. no-cache forces
+        # that revalidation: with Last-Modified but no Cache-Control,
+        # browsers would otherwise cache heuristically and serve stale
+        # pages (e.g. after a theme change) without asking us at all.
         etag = f'"{path}@{node.modified.timestamp()}v{data.version}"'
         if request.headers.get("if-none-match") == etag:
             return Response(status_code=304)
         return HTMLResponse(
             views.render_page(data.menu, path, data.brand, data.custom_css, data.theme, data.favicon),
-            headers={"etag": etag, "last-modified": _http_date(node.modified)},
+            headers={
+                "etag": etag,
+                "last-modified": _http_date(node.modified),
+                "cache-control": "no-cache",
+            },
         )
     if node is not None and node.published and node.content is None:
         # Category label without a landing page: placeholder with the pen
@@ -682,7 +689,10 @@ async def show_page(request: Request, path: str) -> HTMLResponse | Response:
         return HTMLResponse(
             views.render_category(data.menu, path, data.brand, data.custom_css, data.theme, data.favicon),
             404,
-            headers={"last-modified": _http_date(node.modified)},
+            headers={
+                "last-modified": _http_date(node.modified),
+                "cache-control": "no-cache",
+            },
         )
     if node is None and not path:
         # No front page (no top-level node with slug ""): "/" opens the

pagerite/markdown.py

@@ -20,7 +20,7 @@ classes, e.g. `![alt](photo.avif "Caption"){.right}`.
 """
 
 import re
-from datetime import datetime
+from datetime import datetime, timedelta
 
 from markdown_it import MarkdownIt
 from markdown_it.common.utils import escapeHtml
@@ -156,13 +156,12 @@ def render(
 
 
 def _dateline(created: datetime, modified: datetime | None) -> str:
-    """Published/updated line for the ``{dates}`` tag. The updated date is
-    shown only when it falls on a later day than the publication."""
-    pub = f'<time datetime="{created.isoformat()}">{created.day} {created:%B %Y}</time>'
-    out = f"Published {pub}"
-    if modified is not None and modified.date() > created.date():
-        upd = f'<time datetime="{modified.isoformat()}">{modified.day} {modified:%B %Y}</time>'
-        out += f", updated {upd}"
+    """Dateline for the ``{dates}`` tag: "1 Jan 2026", plus
+    " – edited 3 Jan 2026" when the last edit came >= 24h after
+    publishing (quick fixes right after posting stay unmentioned)."""
+    out = f'<time datetime="{created.isoformat()}">{created.day} {created:%b %Y}</time>'
+    if modified is not None and modified - created >= timedelta(hours=24):
+        out += f' – edited <time datetime="{modified.isoformat()}">{modified.day} {modified:%b %Y}</time>'
     return f'<p class="dateline">{out}</p>'