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>

TODO.md

@@ -210,7 +210,7 @@ Construire et envoyer le message XMPP structuré via un compte bot dédié (mess
 
 ### Critères d'acceptation
 - `XmppChannel.send` envoie un message direct formaté (slixmpp mocké en test).
-- Erreur XMPP → `PipelineWarning`, jamais d'exception non gérée.
+- Erreur XMPP → `False` retourné par le canal, le pipeline émet un `PipelineWarning` (jamais d'exception non gérée).
 - Aucun secret dans les logs XMPP.
 
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