The planner proposes bets from unlabelled open issues and the owner's notes, grouped by theme #8850

Follows #8713. Today proposeBets in src/actions/bets.ts groups open issues by their first label only, so unlabelled work and the owner's notes never become a bet.

Done looks like:

• [x] Proposals also group unlabelled open issues by theme: their pillar (the umbrella they hold up), then shared title words. No model call; the same state gives the same proposals (tested).
• [x] An owner note (src/core/app_notes.ts) that names open issues, or shares a theme with them, joins that proposal and is quoted in its journeys.
• [x] Still at most 5 proposals per pass, none repeating a live bet's name, and none with fewer than 2 issues.
• [x] Tests in test/bets.test.ts (or a new file listed in GATE in scripts/gate.ts): an unlabelled pair under one pillar becomes one proposal; a note joins the proposal it names.

Files: src/actions/bets.ts, test/bets.test.ts

Reviewed pull #8870 at its head: ticked Proposals also group unlabelled open issues by theme: their pillar (the umbrella they hold up), then shared title words. No model call; the same state gives the same proposals (tested).; An owner note (src/core/app_notes.ts) that names open issues, or shares a theme with them, joins that proposal and is quoted in its journeys.; Still at most 5 proposals per pass, none repeating a live bet's name, and none with fewer than 2 issues.; Tests in test/bets.test.ts (or a new file listed in GATE in scripts/gate.ts): an unlabelled pair under one pillar becomes one proposal; a note joins the proposal it names..