fix(hls): percent-encode DASH rendition names as one path segment

[kixelated]

Problem

DASH initialization and media URLs placed the rendition name in the path without percent-encoding it. A name containing / became extra path segments, so video/1080p under broadcast live routed to broadcast live/video, rendition 1080p. ?, #, %, and $ break the same URL. The HLS master playlist already encodes each rendition name as one path segment.

Approach

render_representation encodes the name with the HLS renderer's PATH_SEGMENT set, shared from rs/moq-hls/src/export/master.rs rather than copied, then XML-escapes the finished URL. The Representation id stays the raw name (still XML-escaped, not percent-encoded). $Time$ is left literal because only the name is encoded. Rendering and Route::parse cover /, ?, #, %, and $, including video/1080p under live.

Deletes the finished quest.

Impact

• Public API: none. PATH_SEGMENT stays pub(crate).
• Wire: DASH MPD initialization and media URL text changes. Each rendition name is one percent-encoded path segment, using the same RFC 3986 unreserved set as the HLS master. Names that were already a single unreserved segment are unchanged. The Representation id is unchanged. A query string is still XML-escaped once, on the finished URL.

Alternatives

• Copy the percent-encoding set into the MPD renderer. Rejected: the two layouts would drift.
• Percent-encode the whole URL, including $Time$. Rejected: DASH substitutes that token.
• Teach Route::parse to keep a raw slash inside a rendition name. Rejected: a slash is a path separator, so the writer has to encode it.

Follow-ups

None to start. The route parser already decoded a percent-encoded rendition; only the MPD writer was wrong. There is no JS MPD writer. Draft #5083 also edits rs/moq-hls/src/server/routes.rs and may conflict in the test module if it lands first. This branch does not depend on it.

(Written by Grok 4.7)

[kixelated]

Implemented and left as a draft. just check passed. No maintainer decision is outstanding.

I would not start a follow-up that teaches Route::parse to keep a raw slash, a JS MPD writer, or a rebase onto #5083.

(Written by Grok 4.7)

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Reviewing files that changed from the base of the PR and between c6ad626 and 090a3bb.

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📒 Files selected for processing (5)

• quest/m2/README.md
• quest/m2/dash-rendition-uri.md
• rs/moq-hls/src/export/master.rs
• rs/moq-hls/src/export/mpd.rs
• rs/moq-hls/src/server/routes.rs

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-11T01:25:46.989311Z	090a3bb	Draft marked ready
🔒 Security Review	✅ Completed 2026-10-11T01:25:18.961644Z	090a3bb	Draft marked ready

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[kixelated]

Approved to merge 090a3bba319f92518691f10ae0f758c24f381ae0. Existing current-head CI passes; marking the draft ready triggered Codex's independent code and security reviews, both completed with a thumbs up and no review threads.

The DASH renderer now encodes each rendition name as one URL path segment using the shared HLS character set, then XML-escapes the final URL. Representation IDs and the $Time$ placeholder retain their meaning. Public API is unchanged; MPD URL text now encodes reserved characters correctly. No extra fixes or unresolved decisions.

Enqueuing the reviewed head through the merge queue.

(Written by GPT-6)