moq-lite-05: add Path Setup Parameter for URI-less transports

[kixelated]

What

Adds a Path Setup Parameter (0x2) to moq-lite, letting a client convey the request path it wants to reach (origin / relay / virtual host) at connection setup. Modeled on the PATH parameter from draft-ietf-moq-transport-18.

Why

Two of moq-lite's four transport bindings — bare QUIC (binding 1) and Qmux-over-TCP/TLS (binding 3) — negotiate only an ALPN token and have no request URI. Without this parameter, a client on those transports has no way to indicate which path it wants, so a server cannot route the session before broadcasts are exchanged. The URI-bearing bindings (WebTransport's CONNECT path, WebSocket's request URI) already carry it in their handshake.

Details

• New parameter in the Setup Parameter registry: 0x2 | Path | Path (s).
• Value is a non-empty UTF-8 URI path beginning with / ([RFC3986], added as a normative reference).
• Client-only. SETUP is bidirectional in moq-lite, so the asymmetry is stated explicitly: a server MUST NOT send it; a client that receives one closes with PROTOCOL_VIOLATION.
• Required on bindings 1 and 3; forbidden on bindings 2 and 4 (which carry the path in their handshake URI) — a server receiving it there closes with PROTOCOL_VIOLATION.
• Empty/malformed path → PROTOCOL_VIOLATION; unrecognized/unsupported path → session close. Uses moq-lite's existing generic error handling rather than introducing dedicated INVALID_PATH/MALFORMED_PATH codes.
• Relays MUST NOT forward it (per-hop, like other negotiated capabilities).
• Pointer added in the Session section.

Reviewer notes

• The original request was "native QUIC only," but the underlying reason PATH exists ("no handshake URI") applies equally to Qmux-over-TCP/TLS. Scope was deliberately extended to both URI-less bindings (1 and 3) so TCP/TLS sessions aren't left unable to specify a path.
• Spec/doc change only — not built locally (requires the i-d-template toolchain).

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• draft-lcurley-moq-lite.md

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Walkthrough

This pull request adds a Path Parameter capability to the MOQ Lite SETUP protocol. The change introduces a new mechanism for client-to-server communication of request paths in protocol bindings that do not define their own request URI (such as ALPN-only QUIC and Qmux over TCP/TLS). The implementation includes a normative reference to RFC3986, a parameter table entry defining Path as parameter ID 0x2 with string value type, and a complete specification section detailing encoding constraints, required presence/absence by binding type, error-handling behavior, and relay forwarding rules.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main change: adding a Path Setup Parameter to moq-lite for transports without request URIs.
Description check	✅ Passed	The description is detailed and directly related to the changeset, explaining the what, why, and technical details of the Path parameter addition.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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