Adds real-time block detection via ckpool log tailing and a push
channel for the upcoming Svelte UI, all stdlib-only:
- logmon.Tailer follows ckpool.log with rotation/truncation survival
(inode + size tracking) and parses "Solved and confirmed block N"
into BlockEvent values.
- state.Aggregator grows a 256-entry block ring, an OnRefresh hook,
and IngestBlockEvents which best-effort enriches events with the
block hash via bitcoind getblockhash.
- httpapi.Hub implements RFC 6455 from scratch (SHA1 handshake,
unmasked text frames out, masked frames in, ping keepalive,
per-client write mutex, slow-client drop) so we don't pull in a
ws dependency before we can go mod tidy.
- New routes: GET /api/blocks and GET /api/ws. Snapshot pushes fire
on every poll tick and immediately on block-solve.
ZMQ hashblock subscription and SQLite persistence are deferred to
Phase 2b.5 once the s9pk packaging repo exists and we have a real
build environment for adding Go deps.
