protocol: add read_event_index() for SUB 08/F7

Two-step probe+fetch for SUB 08 (EVENT_INDEX), returning the raw 88-byte
(0x58) index block.  SUB_EVENT_INDEX and DATA_LENGTHS[0x08]=0x58 were
already registered — this just wires the method that calls them.

Docstring notes the partially-decoded layout (event count at +3 as uint32 BE,
timestamps at +7) pending live device confirmation.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

minimateplus/protocol.py

@@ -240,6 +240,41 @@ class MiniMateProtocol:
 
     # ── Event download API ────────────────────────────────────────────────────
 
+    def read_event_index(self) -> bytes:
+        """
+        Send the SUB 08 (EVENT_INDEX) two-step read and return the raw 88-byte
+        (0x58) index block.
+
+        The index block contains:
+          +0x00 (3 bytes): total index size or record count — purpose partially
+                           decoded; byte [3] may be a high byte of event count.
+          +0x03 (4 bytes): stored event count as uint32 BE ❓ (inferred from
+                           captures; see §7.4 in protocol reference)
+          +0x07 onwards:   6-byte event timestamps (see §8), one per event
+
+        Caller is responsible for parsing the returned bytes.
+
+        Returns:
+            Raw 88-byte data section (data[11:11+0x58]).
+
+        Raises:
+            ProtocolError: on timeout, bad checksum, or wrong response SUB.
+        """
+        rsp_sub = _expected_rsp_sub(SUB_EVENT_INDEX)
+        length  = DATA_LENGTHS[SUB_EVENT_INDEX]   # 0x58
+
+        log.debug("read_event_index: 08 probe")
+        self._send(build_bw_frame(SUB_EVENT_INDEX, 0))
+        self._recv_one(expected_sub=rsp_sub)
+
+        log.debug("read_event_index: 08 data request offset=0x%02X", length)
+        self._send(build_bw_frame(SUB_EVENT_INDEX, length))
+        data_rsp = self._recv_one(expected_sub=rsp_sub)
+
+        raw = data_rsp.data[11 : 11 + length]
+        log.debug("read_event_index: got %d bytes", len(raw))
+        return raw
+
     def read_event_first(self) -> tuple[bytes, bytes]:
         """
         Send the SUB 1E (EVENT_HEADER) two-step read and return the first