moq-lite-05: sync wire with drafts HEAD (SETUP stream, broadcast epoch, drop cache hint, rename ANNOUNCE)

[kixelated]

Syncs the moq-lite-05 (Lite05Wip / DRAFT_05_WIP) implementation with the latest commits on moq-dev/drafts, across Rust (rs/moq-net), TypeScript (js/net), and the concept docs. All wire changes are gated to lite-05+; older drafts are unaffected.

Drafts covered

Draft PR	Change	Status
#35	Broadcast Epoch + rename ANNOUNCE messages	✅ new
#34	Remove Publisher Cache hint from TRACK_INFO	✅ new
#28	Path Parameter wording (per-hop setup metadata)	✅ docs
#27	Path Setup Parameter for URI-less transports	✅ new
#26	SETUP message + negotiated Probe capability levels	✅ new
#24 / #25 / #32 / #33	Frame Start to FETCH / TRACK stream / drop per-frame duration / fixed-width Hop ID	✅ already landed, re-verified

What changed

#35 — Broadcast Epoch + ANNOUNCE renames

• Wire renames (names only; stream/message IDs unchanged): ANNOUNCE → ANNOUNCE_BROADCAST, ANNOUNCE_INTEREST → ANNOUNCE_REQUEST. Rust types Announce/AnnounceInterest and the JS Announce/AnnounceInterest classes renamed to match (both internal to the private lite module / package surface).
• New per-broadcast Epoch, carried end-to-end. BroadcastInfo.epoch is a SystemTime defaulting to now() (the instant the instance is created), encoded on the wire as milliseconds since 2020‑01‑01 UTC (a varint after the suffix, before the hop chain). JS represents it as the same ms‑since‑2020 number.
• The origin's route selection (route_key) now prefers the newer instance (larger epoch) among equal‑length hop chains, then falls back to the existing deterministic hash tie‑break. Shortest hop chain still wins first, preserving routing; the epoch and hops are forwarded unchanged so a cluster still converges.

#34 — Remove the Publisher Cache hint

• The cache duration is gone from the TRACK_INFO wire message. Retention is now best‑effort, not a guaranteed minimum. The local retention window (model::TrackInfo.cache) stays and falls back to DEFAULT_CACHE on the subscriber.

#26 / #27 — SETUP stream

• New unidirectional Setup Stream (DataType::Setup = 1). Each endpoint opens it once, sends a single SETUP message advertising its capabilities, and FINs. The two SETUPs are independent (neither side blocks on the peer's before opening other streams).
• Probe capability negotiation (None/Report/Increase; unknown future levels saturate to Increase). The subscriber now only opens a PROBE stream if the peer advertised Probe >= Report. Older versions keep probing unconditionally.
• Path Setup Parameter for transports with no request URI. Client::with_path (Rust) sets the path advertised in the client's SETUP; servers never send one. The peer's SETUP (incl. path) is decoded and recorded.
• The SETUP body reuses the parameter framing (the Parameters bag gained typed varint/bytes accessors in Rust; a private mirror in JS).

#28 + concept docs

• doc/concept/layer/moq-lite.md updated: SETUP capabilities + URI‑less path, broadcast epoch convergence, and the cache reframed as a best‑effort local window (it previously referenced the removed SUBSCRIBE_OK field).

Cross-package sync

• rs/moq-net ↔ js/net: mirrored (announce/track wire, the SETUP stream, probe gating). Browser↔relay interop is preserved now that both ends exchange a Setup uni stream.
• doc/concept: updated as above.

Not in scope (follow-up)

• Wiring the received Path into relay routing for URI-less bindings (qmux over TCP/unix). The Path is exchanged and decoded on both ends, but threading it into the relay's origin scoping is a larger native/relay feature left for a separate PR.
• js/net has no multi-route origin tree, so the epoch tie-break is Rust-only there (the JS side decodes the epoch but has nothing to dedup).

Test plan

• cargo test -p moq-net --lib — 396 passed
• cargo test -p moq-relay --lib — 123 passed
• cargo check on hang, moq-relay, libmoq, moq-ffi, moq-mux, moq-bench
• cargo clippy -p moq-net — clean; cargo fmt
• cd js/net && bun test — 189 passed; bun run check (tsc) + biome check clean
• Manual browser↔relay lite-05 smoke test (recommend before merge, since SETUP-stream interop only fully surfaces at runtime)

One design point worth a reviewer's eye: the epoch as SystemTime-now means BroadcastInfo::new() stamps the current wall clock, so two locally-created broadcasts at the same path now resolve by creation time (newer wins) rather than purely by hash. Cross-route/relayed cases are unaffected (epoch is forwarded unchanged).

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(Written by Claude)

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