caciarabot: telegram-shaped photo validation, enforced rule priority, and a lint-found dangling task

caciarabot’s validator already caught a file over Telegram’s upload ceiling, but size is not the only way Telegram refuses a photo: width and height above 10000 px, or a longer side more than 20× the shorter, fails with PHOTO_INVALID_DIMENSIONS even at a few hundred KB — and a panorama or tall screenshot is exactly the file people drop in. A new telegram/imagesize.py reads the dimensions out of the header with the standard library alone — PNG (IHDR), JPEG (skip the APPn segments to the start-of-frame marker) and all three WebP variants — checked against macOS sips on all 142 real images in media/ with no false positives (b06e315).

priority was parsed, accepted by the schema, and never read by decision.select, so a rule author could set it and nothing happened; selection now stable-sorts the firing rules by priority after the shuffle, with a high-priority rule that loses its probability roll stepping aside rather than silencing lower ones (c32563c). Adding ruff to CI (with RUF006) found the daily-thought and digest loops started with a bare asyncio.create_task() holding no reference — asyncio keeps tasks only weakly, so such a task can be garbage-collected mid-run, and anything escaping the loop ended it silently with the bot never posting again (62c3302). The digest no longer discards the day when generation fails: config/fallback/digest.txt holds twelve canned comments that rotate through the existing no-repeat machinery and say nothing about a link the bot never read, with no retry, since a 429 means the quota is gone (67887df).