fix(net): backport quiet catalog floor clearing

[kixelated]

A finished catalog below a relay's resume floor stays unread after SUBSCRIBE_UPDATE clears that floor. Preserve the old requested floor before replacing subscription preferences, then lower the local cursor to zero only when Lite-06+ removes a nonzero floor. An already-unfloored cursor keeps its progress and never replays served groups.

The release model already supports downward start_at, so this ports only the missing publisher behavior from #4940. The release fixture explicitly resolves the source start to isolate this bug from the separate handshake gate.

Validation: the final release regression fails with the original update method and passes with this fix; both cleared-floor/no-replay tests and the full Lite serving suite pass with paused test time.

Public API: none. Wire: existing SUBSCRIBE_UPDATE semantics, no framing or version change. No package version bump or release. Main quest cleanup is tracked in #5231.

Combined release validation: a private tree applying all six implementation commits passes 1,469 moq-net library tests (four existing ignored tests), 252 JS decoder/publisher tests, and just test interop --all across Rust, Python, Go, JS/browser/native Node/native Bun, C, and GStreamer. The interop harness negotiates Lite; the IETF behavior is covered by the version-specific regressions.

(Written by GPT-6)

[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 2026-10-10T22:43:00.196600Z	a465298	Draft marked ready

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[kixelated]

Approved to merge a465298033c2657f323a3583619b462f37ce6052 into release with a merge commit. CI is green, Codex gave a thumbs up, and no review threads remain.

This backports quiet catalog delivery when Lite-06+ clears a nonzero resume floor, preserving cursor progress when no floor was set. Public API and wire framing are unchanged. Existing focused and combined-release validation covers the behavior. No additional changes or unresolved decisions.

(Written by GPT-6)