quest(moxygen): block the line on the #4276 group fetch fill findings

[kixelated]

Problem

#4276 merged into this line with three Codex P2 findings unanswered. Maintainer decisions from the 09-28 merged-PR audit: each blocks the line from landing on main.

Approach

New child quest Group fetch fill on the moxygen line, covering:

• A truncated fetch stream is cached as a complete group, since FETCH_OK's end_location is never checked (r4113942736). For a whole-group request, where end_location is only the requested boundary, the quest requires a concrete complete-group signal.
• A first fetch object with no IDs is accepted by the (false, None | Some(1)) arm (r4113942737).
• The upstream group FETCH asks from object 0, ignoring the request's frame_start (r4113942733).

All three verified still present on the line branch.

The README also records the three declines the maintainer accepted, so they are not reopened: mid-group FETCH start (r4113671550), FETCH_OK naming the requested end (r4114050992), and the ignored contradictory End of Track (r4114051032).

No blocker for the #4273 priority default: quest/m1/signed-priority.md on main already covers it.

Impact

• Quest files only. No API or wire change.

Alternatives

• One quest per finding. Rejected: all three touch the same fill path in ietf/subscriber.rs and would conflict.

Follow-ups

• None beyond the new quest.

(Written by Claude Opus 5.5)

🤖 Generated with Claude Code

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Codex Review Summary

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

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-29T19:21:32.072868Z	1cee2e1	New commits

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[kixelated]

Verdict: MERGE

Positive improvement and well-scoped for a line-blocking quest. The three #4276 findings are concrete, still present on the line, and grouped correctly (same ietf/subscriber.rs fill path) rather than split into conflicting child quests.

• Truncation vs FETCH_OK.end_location, anonymous first-object acceptance, and ignoring frame_start on the upstream FETCH are each named with a file/behavior fix and a regression test expectation.
• Maintainer-accepted declines (mid-group FETCH start, FETCH_OK naming the requested end, contradictory End of Track) are recorded so they are not reopened — good hygiene.
• Complexity is justified: quest docs only, no premature API/wire change.

Worth landing so the moxygen line cannot ship the incomplete fill.

This is an automated review, not the maintainer's decision
(Written by Grok)

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