docs(M10): align GUIDE §10 and TODO.md with real slixmpp API and D6 contract

GUIDE_DEV_PYTHON.md §10 corrections:
- Fix XmppSettings defaults (host="", resource="pronote-sync")
- Replace Google-style docstrings with Sphinx/reST in examples
- Document connect(host, port) returning asyncio.Future, remove process() reference
- Document TLS mapping: use_tls=True → direct TLS, use_tls=False → STARTTLS
- Fix factory signature: get_channel(XmppSettings, dry_run) -> Channel | None
- Document Channel.send() -> bool never raises PipelineWarning (D6)
- Fix duplicate §10.3 numbering → §10.3-§10.6
- Remove pronote_messages duplication in M11 example
- Document JID with resource construction
- Document enriched message format (date, change types, times, due date, author)

TODO.md M10:
- Adjust acceptance criterion: channel returns False, pipeline emits PipelineWarning

.secrets.baseline:
- Line numbers updated for documentation shifts

Co-authored-by: opencode/tech-writer <tech-writer@agents.invalid>

.secrets.baseline

@@ -140,7 +140,7 @@
         "filename": "GUIDE_DEV_PYTHON.md",
         "hashed_secret": "90bd1b48e958257948487b90bee080ba5ed00caa",
         "is_verified": true,
-        "line_number": 4935,
+        "line_number": 5029,
         "is_secret": false
       }
     ],
@@ -177,5 +177,5 @@
       }
     ]
   },
-  "generated_at": "2026-09-07T17:59:08Z"
+  "generated_at": "2026-09-08T00:29:02Z"
 }