fix: recover one hotlinked image, retire the other eleven

Twelve images across seven articles were hotlinked from servers that no longer
exist, so they were broken on the live sites. Checked every one against the
Wayback Machine, patiently enough to trust the answer: an earlier pass appeared
to find seven, but that was a test treating an empty response as a hit.

One survives. visualberlin.org's p1010789, a 2011 capture of the projector set
up against Mannheim city hall during the Flimmerkiste wildscreening, is now a
local asset in flux.vision/content/library/ and the reference points at it.

The other eleven were never captured. Both dead domains are archived, so this is
not a gap in coverage: of 8,438 visualberlin.org URLs and 204 for mutanten.org,
only that one image is there. mutanten.org's archive does not reach back to its
fp-content era at all, which is where the Logan's Run stills lived.

So lostimages.py learns about dead hosts, which it matches rather than fetching,
because a build must not depend on the network and a dead host is a fact about
the world rather than about the document. The references stay in the Markdown,
as the existing ones do: the reference records what was there.

It matters more on the capsule than on the web. A browser shows a broken image
as a silent gap, but gemtext has no inline images, so every one becomes a
visible => link line and the page would advertise a dead host as somewhere worth
going. smolnet.py therefore strips them too, reading the same host list, since
it works on the Markdown source and never sees Pelican's output.

lostimages.py moves to the repo-level plugins/ directory beside smolnet. It was
shared already, with flux.vision reaching into tobias.raayoni-last.com for it,
and randogoth.com now needs it too; a shared plugin living inside one site was
the wrong shape for three consumers.

Left alone deliberately: the two mutanten.org links in mutantenkino-website.md.
That entry is about having built the site, so the link is its subject rather
than decoration, and a dead link does not make the record wrong.

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

plugins/smolnet.py

@@ -69,6 +69,12 @@ INTERNAL = re.compile(r"\{(filename|static|attach)\}([^)\s]+)")
 
 SUMMARY_MARKER = "<!-- PELICAN_END_SUMMARY -->"
 
+# Markdown image syntax, for dropping the ones whose host is gone. Matched on
+# the source rather than the rendered HTML because this plugin reads the
+# Markdown directly, so lostimages.py, which works on Pelican's output, never
+# sees the capsule.
+MD_IMAGE = re.compile(r'!\[[^\]]*\]\(\s*(https?://[^\s)]+)[^)]*\)')
+
 
 def rot13(text):
     """The obfuscation used on addresses in the HTML templates."""
@@ -156,6 +162,32 @@ def reveal_rot13(text, attr):
     return "".join(out)
 
 
+def drop_dead_images(text, dead):
+    """Remove images hotlinked from hosts that no longer exist.
+
+    It matters more here than on the web. A browser shows a broken image as a
+    silent gap, but gemtext has no inline images: every one becomes a visible
+    `=>` link line, so the page would advertise a dead host as though it were
+    somewhere worth going.
+
+    Shares LOSTIMAGES_DEAD_HOSTS with lostimages.py so there is one list, and
+    matches on the host rather than fetching, because a build must not depend on
+    the network.
+    """
+    if not dead:
+        return text
+
+    def sub(match):
+        host = match.group(1).split("//", 1)[1].split("/")[0].lower().split(":")[0]
+        if any(host == d or host.endswith("." + d) for d in dead):
+            return ""
+        return match.group(0)
+
+    text = MD_IMAGE.sub(sub, text)
+    # a line that held nothing but the dropped image would leave a blank
+    return re.sub(r"\n[ \t]*\n[ \t]*\n+", "\n\n", text)
+
+
 def toml_escape(value):
     return str(value).replace("\\", "\\\\").replace('"', '\\"')
 
@@ -193,6 +225,8 @@ class CapsuleGenerator(Generator):
         order = s.get("SMOLNET_SECTION_ORDER", {}) or {}
         latest_n = s.get("SMOLNET_LATEST", 15)
         rot_attr = s.get("SMOLNET_ROT13_ATTR")
+        dead_hosts = {h.lower().lstrip(".") for h in
+                      s.get("LOSTIMAGES_DEAD_HOSTS", [])}
         sidecar_name = s.get("SMOLNET_SIDECAR", ".itsybitsy.toml")
 
         articles = [a for a in self.context.get("articles", [])]
@@ -214,6 +248,7 @@ class CapsuleGenerator(Generator):
             body = body.replace(SUMMARY_MARKER, "")
             body = rewrite_internal(body, by_source, self._warn)
             body = reveal_rot13(body, rot_attr)
+            body = drop_dead_images(body, dead_hosts)
             # Blank lines, not newlines: a heading and the line under it are
             # separate blocks only if a blank line divides them, otherwise the
             # date runs into the first sentence as one paragraph.