fix: parse XML-format cleanup tags and strip from SSE stream

The model emits cleanup ops as XML elements (<drop>block:x</drop>,
<release handle="x"/>, <collapse>turns N-M "summary"</collapse>)
but the parser only handled prose format (drop: block:x). Add XML
regex matchers alongside the existing prose parser so both formats
are recognized, executed, and stripped from the streaming output.

src/mnemosyne/tags.py

@@ -22,6 +22,7 @@ from dataclasses import dataclass, field
 @dataclass
 class CollapseOp:
     """A turn-range collapse: replace multiple turns with a summary."""
+
     start_turn: int
     end_turn: int
     summary: str
@@ -30,6 +31,7 @@ class CollapseOp:
 @dataclass
 class CleanupOps:
     """Parsed cleanup operations from a <memory_cleanup> tag."""
+
     drops: list[str] = field(default_factory=list)
     summaries: list[tuple[str, str]] = field(default_factory=list)
     anchors: list[str] = field(default_factory=list)
@@ -38,8 +40,7 @@ class CleanupOps:
 
     @property
     def empty(self) -> bool:
-        return not (self.drops or self.summaries or self.anchors
-                    or self.releases or self.collapses)
+        return not (self.drops or self.summaries or self.anchors or self.releases or self.collapses)
 
     def __str__(self) -> str:
         parts = []
@@ -65,67 +66,95 @@ _TAG_PATTERN = re.compile(
 # Match tensor/block ID references: tensor:xxxxxxxx or block:xxxxxxxx (8-12 hex chars)
 _BLOCK_ID = re.compile(r"(?:tensor|block):([a-f0-9]{8,12})(?![a-f0-9])")
 
-# Match summarize with quoted summary text
+# Match summarize with quoted summary text (prose format)
 _SUMMARIZE_PATTERN = re.compile(
     r'summarize:\s*(?:tensor|block):([a-f0-9]{8,12})(?![a-f0-9])\s+"([^"]*)"'
 )
 
-# Match release with comma-separated paths
+# Match release with comma-separated paths (prose format)
 _RELEASE_PATTERN = re.compile(r"release:\s*(.+)")
 
 # Match collapse with turn range and quoted summary
 # Format: collapse: turns 3-8 "Summary of what happened in those turns"
-_COLLAPSE_PATTERN = re.compile(
-    r'collapse:\s*turns\s+(\d+)\s*-\s*(\d+)\s+"([^"]*)"'
-)
+# Also: <collapse>turns 3-8 "Summary"</collapse>
+_COLLAPSE_PATTERN = re.compile(r'collapse[\s:>]+turns\s+(\d+)\s*-\s*(\d+)\s+"([^"]*)"')
+
+# --- XML element variants (model sometimes uses XML instead of prose) ---
+# <drop>block:4ab5ee7a</drop> or <drop>tensor:4ab5ee7a</drop>
+_XML_DROP = re.compile(r"<drop>(?:tensor|block):([a-f0-9]{8,12})</drop>")
+# <release handle="abc123"/> or <release handle="abc123" reason="..."/>
+_XML_RELEASE = re.compile(r'<release\s+handle="([a-f0-9]{8,12})"')
+# <anchor>block:abc123</anchor>
+_XML_ANCHOR = re.compile(r"<anchor>(?:tensor|block):([a-f0-9]{8,12})</anchor>")
+# <summarize id="abc123">summary text</summarize>
+_XML_SUMMARIZE = re.compile(r'<summarize\s+id="([a-f0-9]{8,12})"[^>]*>([^<]*)</summarize>')
+# <collapse>turns 3-8 "Summary"</collapse>
+_XML_COLLAPSE = re.compile(r'<collapse>turns\s+(\d+)\s*-\s*(\d+)\s+"([^"]*)"</collapse>')
 
 
 def parse_cleanup_tags(text: str) -> CleanupOps:
-    """Extract cleanup operations from text containing <memory_cleanup> tags.
+    """Extract memory operations from ``<memory_cleanup>`` blocks.
 
-    Returns a CleanupOps with all parsed operations. Multiple tags in
-    the same text are merged into a single CleanupOps.
+    Supports both prose format (``drop: block:abc``) and XML element
+    format (``<drop>block:abc</drop>``).
     """
     ops = CleanupOps()
 
     for match in _TAG_PATTERN.finditer(text):
         body = match.group(1)
+
+        # --- XML element variants (scan full body first) ---
+        for m in _XML_DROP.finditer(body):
+            ops.drops.append(m.group(1))
+        for m in _XML_RELEASE.finditer(body):
+            ops.releases.append(m.group(1))
+        for m in _XML_ANCHOR.finditer(body):
+            ops.anchors.append(m.group(1))
+        for m in _XML_SUMMARIZE.finditer(body):
+            ops.summaries.append((m.group(1), m.group(2)))
+        for m in _XML_COLLAPSE.finditer(body):
+            ops.collapses.append(
+                CollapseOp(
+                    start_turn=int(m.group(1)),
+                    end_turn=int(m.group(2)),
+                    summary=m.group(3),
+                )
+            )
+
+        # --- Prose line-based format ---
         for line in body.splitlines():
             line = line.strip()
-            if not line:
+            if not line or line.startswith("<"):
                 continue
 
-            # Summarize (must check before drop — both start with block ID)
             m = _SUMMARIZE_PATTERN.match(line)
             if m:
                 ops.summaries.append((m.group(1), m.group(2)))
                 continue
 
-            # Drop
             if line.startswith("drop:"):
                 m = _BLOCK_ID.search(line)
                 if m:
                     ops.drops.append(m.group(1))
                 continue
 
-            # Anchor
             if line.startswith("anchor:"):
                 m = _BLOCK_ID.search(line)
                 if m:
                     ops.anchors.append(m.group(1))
                 continue
 
-            # Collapse (turn range)
             m = _COLLAPSE_PATTERN.match(line)
             if m:
-                ops.collapses.append(CollapseOp(
-                    start_turn=int(m.group(1)),
-                    end_turn=int(m.group(2)),
-                    summary=m.group(3),
-                ))
+                ops.collapses.append(
+                    CollapseOp(
+                        start_turn=int(m.group(1)),
+                        end_turn=int(m.group(2)),
+                        summary=m.group(3),
+                    )
+                )
                 continue
 
-            # Release
             m = _RELEASE_PATTERN.match(line)
             if m:
                 paths = [p.strip() for p in m.group(1).split(",") if p.strip()]