No page can poll on a timer: the unused data-live-every beat leaves the client #10789

Intent: the owner hates pages refreshing on a clock; live regions refresh on events only. src/web/client.ts still carries data-live-every (the arm/beats interval around line 2535) though no page in src/ emits that attribute any more (grep finds it only in client.ts and tests).

• [x] The data-live-every branch, its beats map and its interval leave src/web/client.ts; event-driven refresh (data-live, data-live-src, etag swap) is unchanged.
• [x] test/no-polling.test.ts drops client.ts's allowance for data-live-every (keeping setInterval only for the clocks that redraw text) so a page or client that reintroduces it fails.
• [x] The data-live-every case in test/live-pages.test.ts is removed with its mechanism, and the other test files that mention it (check-shard-event, boards-store, pull-checks-line-route) are read and updated only where they assert the attribute is emitted; say which in the pull.
• [x] The page script shrinks; the pull gives its byte count before and after.

Files: src/web/client.ts, test/no-polling.test.ts, test/live-pages.test.ts. Risks: confirm with a grep of src/ and the rendered pages that nothing emits the attribute before removing it. Suggested brief: mason.

Reviewed pull #10817 at its head: ticked The data-live-every branch, its beats map and its interval leave src/web/client.ts; event-driven refresh (data-live, data-live-src, etag swap) is unchanged.; test/no-polling.test.ts drops client.ts's allowance for data-live-every (keeping setInterval only for the clocks that redraw text) so a page or client that reintroduces it fails.; The data-live-every case in test/live-pages.test.ts is removed with its mechanism, and the other test files that mention it (check-shard-event, boards-store, pull-checks-line-route) are read and updated only where they assert the attribute is emitted; say which in the pull.; The page script shrinks; the pull gives its byte count before and after..