Add Server/Last-Modified headers and a {dates} dateline tag

An http middleware sets 'Server: pagerite' (dropping uvicorn's versioned
default) and content pages return Last-Modified from Node.modified. In
markdown, a {dates} line expands to the article's published/updated
dateline (updated shown only when it falls on a later day); the editor
preview resolves it for pages that exist, unsaved pages show it literal.
Demonstrated in the long-read seed page.

AGENTS.md

@@ -89,8 +89,11 @@ not for the public pages. See `docs/design-principles.md` for the design.
     on every page, otherwise browsers fall back to the build's
     `/favicon.ico` by convention.
   - `markdown.py` — markdown-it-py renderer (html passthrough + attrs,
-    footnote, deflist, tasklists plugins). Custom image rule: relative srcs
-    resolve against the page path, titled images become figures.
+    footnote, deflist, tasklists plugins; typographer + breaks on). Custom
+    image rule: relative srcs resolve against the page path, titled images
+    become figures. A `{dates}` line expands to the article's
+    published/updated dateline (`p.dateline`, from `Node.created`/
+    `modified`; left literal in previews of unsaved pages).
   - `views.py` — the shared page layout as an html5tagger `Template` with
     placeholders (`Title`, `Brand`, `Banner`, `Nav`, `Sidebar`, `Main`), nav
     rendering straight from the `Data.menu` tree (siblings sorted by

frontend/src/assets/pagerite.css

@@ -777,6 +777,14 @@ body.editing:has(.multicol) img.wide:not(figure img) {
   list-style: none;
 }
 
+/* Published/updated line, expanded from the {dates} tag in the markdown
+   (typically placed right after the article's h1). */
+.dateline {
+  color: var(--muted);
+  font-size: 0.85rem;
+  text-align: left;
+}
+
 .footnote {
   font-size: 0.85rem;
   color: var(--muted);

pagerite/app.py

@@ -18,6 +18,7 @@ import re
 from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
 from datetime import UTC, datetime
+from email.utils import format_datetime
 from pathlib import Path
 
 import blake3
@@ -154,6 +155,14 @@ app = FastAPI(
 )
 
 
+@app.middleware("http")
+async def _headers(request: Request, call_next) -> Response:
+    """Replace uvicorn's default Server header with ours (no version)."""
+    response = await call_next(request)
+    response.headers["server"] = "pagerite"
+    return response
+
+
 class PageIn(BaseModel):
     """Payload for creating or replacing a page."""
 
@@ -471,6 +480,11 @@ async def delete_page(path: str) -> None:
 _SLUG_RE = re.compile(r"^[a-z0-9][a-z0-9_-]*$")
 
 
+def _http_date(dt: datetime) -> str:
+    """RFC 7231 date for the Last-Modified header."""
+    return format_datetime(dt.astimezone(UTC), usegmt=True)
+
+
 def _is_reserved(path: str) -> bool:
     """Slug shape that content may never use: each segment must be lower-case
     ASCII letters, digits, hyphens and underscores (underscores may not be
@@ -542,10 +556,17 @@ async def editor_ws(ws: WebSocket) -> None:
                     })
                 case "render":
                     markdown = msg.get("markdown", "")
+                    chain = resolve(data.menu, path)
+                    node = chain[-1] if chain else None
                     await ws.send_json({
                         "type": "html",
                         "path": path,
-                        "html": render(markdown, path),
+                        "html": render(
+                            markdown,
+                            path,
+                            node.created if node else None,
+                            node.modified if node else None,
+                        ),
                         "has_h1": has_h1(markdown),
                     })
                 case "save":
@@ -653,12 +674,16 @@ async def show_page(request: Request, path: str) -> HTMLResponse | Response:
             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},
+            headers={"etag": etag, "last-modified": _http_date(node.modified)},
         )
     if node is not None and node.published and node.content is None:
         # Category label without a landing page: placeholder with the pen
         # to create it (404 — no page here, but the node is real).
-        return HTMLResponse(views.render_category(data.menu, path, data.brand, data.custom_css, data.theme, data.favicon), 404)
+        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)},
+        )
     if node is None and not path:
         # No front page (no top-level node with slug ""): "/" opens the
         # first item of the navigation instead.

pagerite/markdown.py

@@ -20,6 +20,7 @@ classes, e.g. `![alt](photo.avif "Caption"){.right}`.
 """
 
 import re
+from datetime import datetime
 
 from markdown_it import MarkdownIt
 from markdown_it.common.utils import escapeHtml
@@ -135,9 +136,34 @@ md.core.ruler.push("unwrap_lone_figures", _unwrap_lone_figures)
 md.core.ruler.push("tag_task_checkboxes", _tag_task_checkboxes)
 
 
-def render(text: str, page_path: str = "") -> str:
-    """Render Markdown text to an HTML string."""
-    return md.render(text, {"page_path": page_path})
+def render(
+    text: str,
+    page_path: str = "",
+    created: datetime | None = None,
+    modified: datetime | None = None,
+) -> str:
+    """Render Markdown text to an HTML string.
+
+    A ``{dates}`` line expands to the article's published/updated dateline
+    (needs ``created``/``modified``; left as-is in contexts without them,
+    e.g. the editor preview). Position is the author's choice — typically
+    right after the article's h1.
+    """
+    html = md.render(text, {"page_path": page_path})
+    if created is not None and "<p>{dates}</p>" in html:
+        html = html.replace("<p>{dates}</p>", _dateline(created, modified))
+    return html
+
+
+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}"
+    return f'<p class="dateline">{out}</p>'
 
 
 def has_h1(text: str) -> bool:

pagerite/seed.py

@@ -77,6 +77,8 @@ def render(text: str, page_path: str) -> str:
 LONG_READ = """\
 *An essay long enough to scroll, to demonstrate the gentle reveal of headings, figures and code blocks as they enter the viewport.*
 
+{dates}
+
 ![Layered dunes](dunes.svg "Full-width artwork between sections"){.wide}
 
 ## Chapter one

pagerite/views.py

@@ -366,7 +366,10 @@ def page_content(menu: dict[str, Node], path: str) -> HTML:
         # only rendered as h1 when the markdown has none of its own.
         if not has_h1(node.content or ""):
             doc.h1(node.title)
-        doc.div(HTML(render(node.content or "", path)), class_="body")
+        doc.div(
+            HTML(render(node.content or "", path, node.created, node.modified)),
+            class_="body",
+        )
     return HTML(str(doc))