fix: cap listener connections, serve HEAD, fix feed parser CR round-trip

core/src/feed.rs

@@ -96,8 +96,14 @@ impl Feed {
     }
 
     pub fn parse(text: &str) -> Feed {
+        // Trailing CRs are line endings, never content: `str::lines` strips
+        // only one CR before a newline, so a CR run would survive one parse
+        // and partly vanish on the next, breaking the render fixpoint.
         Feed {
-            items: text.lines().map(parse_line).collect(),
+            items: text
+                .lines()
+                .map(|line| parse_line(line.trim_end_matches('\r')))
+                .collect(),
         }
     }
 
@@ -424,4 +430,34 @@ mod tests {
             self.meta("nick")
         }
     }
+
+    /// xorshift: deterministic pseudo-randomness, dependency-free.
+    fn next(seed: &mut u64) -> u64 {
+        *seed ^= *seed << 13;
+        *seed ^= *seed >> 7;
+        *seed ^= *seed << 17;
+        *seed
+    }
+
+    #[test]
+    fn parse_never_panics_and_render_reaches_a_fixpoint() {
+        // Hostile pieces in random order: the parser must survive anything,
+        // and whatever it accepts must render to a form that re-parses to
+        // itself, so a store save can never corrupt a feed it loaded.
+        let pieces = [
+            "# ", "# key = value\n", "smol:mail ", "smol:repost ", "\t", "\n", "---\n",
+            "2026-10-01T12:47:00Z", "a", "mfrggzdfmztwq2lknnwg23tpoa3...", "/", "\u{e9}",
+            "\r", " ", "#\n", "smol:host_key = ",
+        ];
+        let mut seed = 0x5eed_1234_u64;
+        for _ in 0..2000 {
+            let n = (next(&mut seed) % 48) as usize;
+            let input: String = (0..n)
+                .map(|_| pieces[(next(&mut seed) % pieces.len() as u64) as usize])
+                .collect();
+            let once = Feed::parse(&input).render();
+            let twice = Feed::parse(&once).render();
+            assert_eq!(once, twice, "render must be a fixpoint after parse");
+        }
+    }
 }