Contract 7.3.0

Jamie's pre-beta follow-ups (feedback #342 and the journey r3 open questions).

• An incomplete Path of Legends board is re-read, not kept: a full board whose cutoff fell 40 or more below the previous snapshot's is flagged at ingest and read once more about 30 minutes later, and the re-read replaces it for every reader (the flagged snapshot is kept, marked superseded). The daily read stays at 10:00Z (#342).
• Every response carries notes and docs: elixir_examples {example} serves notes and elixir_docs {query} a docs pointer to the best match's page, and a tool with nothing to say serves notes: []. Every output schema now requires both.
• cards_card season.forms[].players counts each form's distinct players (it was null on a custom window).
• The timeline's clan activity note says why clans_standings counts more over the same window: per member (a friendly between two members counts on both rows), by play time, and today's members including a joiner's battles for another clan.
• A season finalised in the last three days is rolled again each night, so battles from its last hours that arrive late reach the season meta.

Additive; notes and docs are now always present.