Return structured errors for interrupted data sync transfers

[rudycelekli]

HTTP response headers can arrive before a body read fails. Translate IncompleteRead and connection-reset body failures into the existing machine-readable DataSyncError response (503), for both manifests and artifacts. Only remote reads are wrapped; local disk-write failures remain distinct, and partial response content is excluded from the public error message.

A first initialization has no local release to reuse, so an unsolicited HTTP 304 must also be a structured remote error. Existing conditional ETag reuse remains supported.

All five new regressions fail before the fix; the focused data-sync suite passes 25 tests afterward. Tests also verify active data remains usable and lock/download scratch are removed. Deliberately removing the read-error conversion or restoring unconditional 304 acceptance makes the corresponding regressions fail.

Full clean-checkout validation

Exact signed head: 34ca432b59beaa6f33659c97640a2c93cace5581. Recursive paper submodule initialized at its repository-pinned commit. All six required commands pass:

• ruff check .
• ruff format --check .
• benchmark-radar normalize-catalog
• benchmark-radar classify
• benchmark-radar build-data-release
• pytest -q: 1470 passed, no skipped tests

The rebuilt corpus retains 3,212 records, five sources, and 67 snapshots. Generated outputs are not committed. Signed commit with DCO sign-off. GitHub checks are separate from these local results.

[rudycelekli]

Agent-authored PR annotation: 330226 GPT.

[ktwu01]

Closing as not planned. One author now has a cap of 10 open issues + PRs, and this account had 56 open PRs and 11 open issues, mostly paired with each other. We merged the three changes that fix silent data loss in the corpus (#723, #774, and #773 once rebased) and are closing the rest so review stays possible.

This is not a verdict that the change is wrong. If you think this one matters, reopen it later when you are under the cap, one at a time, with a reproduction from a real user or caller rather than a hypothetical edge case.

不是否定这个改动本身。为保证评审能跟上，同一作者最多同时保留 10 个未关闭的 issue/PR；该账号曾有 56 个未关闭 PR 和 11 个 issue。已合并修复语料静默丢失的三个改动，其余先关闭。若认为本条重要，请在低于上限后逐个重新打开，并附真实用户或调用方的复现。

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