Add Matrix intake bot (M1+M2): typed message → approved fundraising-grid write

New backend/matrix_intake/ runs as its own process (matrix-nio isolated from the
stdlib CRM): local-Qwen parse via Spark Control → in-thread human approval
(yes/edit/no) → write through the CRM's own log-communication endpoint, tagged
source=matrix_intake. Adds read-only GET /api/intake/match (returns grid row id,
no-duplicate contract); threads provenance through handle_log_fundraising_communication.
Reviewer-passed: pop-before-commit closes a double-approve race; edit-grammar fix.
Text-only v1; business-card photo (M3) deferred (no Spark vision model).
26/26 tests green; live Matrix smoke pending deploy.

backend/matrix_intake/matrix_io.py

@@ -0,0 +1,55 @@
+"""Matrix plumbing lifted from matrix-bridge (src/bot.py): message splitting, thread-root
+detection, and a threaded-reply sender. Kept dependency-light so the rest of the bot is
+testable without a live homeserver."""
+
+MAX_MSG_CHARS = 30000  # well under Matrix's ~64KB event cap
+
+
+def split_message(text, limit=MAX_MSG_CHARS):
+    """Split text into <=limit-char chunks on newline boundaries (no truncation)."""
+    if len(text) <= limit:
+        return [text]
+    chunks, buf = [], ""
+    for line in text.splitlines(keepends=True):
+        while len(line) > limit:
+            if buf:
+                chunks.append(buf)
+                buf = ""
+            chunks.append(line[:limit])
+            line = line[limit:]
+        if len(buf) + len(line) > limit:
+            chunks.append(buf)
+            buf = ""
+        buf += line
+    if buf:
+        chunks.append(buf)
+    return chunks
+
+
+def thread_root_of(event):
+    """Return the thread root event_id if this message is a threaded reply, else None."""
+    relates = (getattr(event, "source", None) or {}).get("content", {}).get("m.relates_to") or {}
+    if relates.get("rel_type") == "m.thread":
+        return relates.get("event_id")
+    return None
+
+
+def thread_content(text, thread_root):
+    """Build an m.room.message content dict, threaded under thread_root when given."""
+    content = {"msgtype": "m.text", "body": text}
+    if thread_root:
+        content["m.relates_to"] = {
+            "rel_type": "m.thread",
+            "event_id": thread_root,
+            "is_falling_back": True,
+            "m.in_reply_to": {"event_id": thread_root},
+        }
+    return content
+
+
+def make_say(client):
+    """Return an async say(room_id, text, thread_root=None) bound to a matrix-nio client."""
+    async def say(room_id, text, thread_root=None):
+        for chunk in split_message(text):
+            await client.room_send(room_id, "m.room.message", thread_content(chunk, thread_root))
+    return say