Harden session lifecycle, timers, and canonical room routing

[Andyccr]

Full architecture audit after #9. This PR hardens the remaining lifecycle, timer, and navigation gaps without changing the v1 wire or leaving the static Pages constraint.

What was wrong

• Failed joins left a live transport; retry stacked connections.
• Outbound ack timers kept running while the tab was hidden (false 未送达 on mobile).
• Presence prune treated ICE-connected quiet peers as gone.
• Room names were raw in lobby/hash/recent and normalized only on parse — tab highlight and share URLs drifted.
• go() raced hashchange and could double-open; empty room names were joinable; App catch clobbered relay diagnostics.

What changed

• Session teardown + epoch — join always leaves the previous transport; in-flight send/ping/payload ignore stale generations.
• Visibility-aware Outbound — deadlines pause while hidden, then settle remaining time on resume.
• Presence prune — skip ids still in transport.peerIds().
• Payload router — applyIncoming dispatches hello/typing/ack/chat.
• Canonical RoomSpec — one name at lobby, jump, hash, recent, and RoomManager. Empty names rejected.
• Single hash pipeline — go() only writes the hash; hashchange routes.
• Debounced log cache — snapshot ~2s after new lines, not only on leave.
• Jump dialog shows 口令 copy, respects canJoin(), nick commits before send.

Still static GitHub Pages, public WebTorrent/Nostr, no TURN, no libp2p, no PWA, no protocol v2.

Test plan

• npm test (62 tests)
• npm run build:pages
• Join 茶 室 from lobby → URL and tab use 茶-室
• Empty room name does not join
• Two windows: send, 送达; background a tab during pending ack and confirm it does not immediately fail