feat(rc-multipart): list and abort incomplete uploads

[cxymds]

Related work

• Refs rustfs/backlog#1366
• Blocked by rustfs/backlog#1384
• Depends on feat(rc-output): introduce output schema v3 #266
• Depends on feat(cli)!: add runtime discovery and replication workflows #272

Background

RustFS 1.0.0-beta.10 exposes S3 multipart list and abort operations, but its ListMultipartUploads implementation interprets prefix as an exact object key. Bucket-wide, prefix, and recursive cleanup therefore cannot be implemented safely until rustfs/backlog#1384 is resolved.

This PR delivers the safe exact-key subset now and returns a typed unsupported-feature result before alias or network resolution for the affected modes. It intentionally does not close rustfs/backlog#1366 because recursive acceptance remains blocked by the server issue.

Solution

• Add typed multipart upload records, paginated list options/results, identities, and abort requests to the rc-core object-store boundary.
• Preserve source compatibility for external and mock ObjectStore implementations by providing default UnsupportedFeature bodies for the new trait methods.
• Implement ListMultipartUploads and AbortMultipartUpload in rc-s3, including metadata mapping, retries, idempotent exact 404 NoSuchUpload handling, and defensive pagination validation.
• Support rc ls alias/bucket/key --incomplete for one exact object key with deterministic human and output-v3 JSON results.
• Support rc rm alias/bucket/key --incomplete for exact-key abort, dry-run planning, bounded concurrency, retry, deterministic ordering, and complete per-upload success/failure retention.
• Reject bucket, prefix, and recursive incomplete-upload modes with a typed unsupported-feature result linked to rustfs/backlog#1384.
• Emit output-v3 multipart listing, cleanup, typed error, and partial envelopes; partial cleanup retains both successful and failed upload records.
• Inherit the explicit-stack async command launcher from feat(cli)!: add runtime discovery and replication workflows #272; this PR has no crates/cli/src/main.rs delta relative to its base.
• Make the local S3 subprocess test server explicitly switch accepted sockets to blocking mode for cross-platform reliability.

RustFS beta.10 compatibility and safety

• A truncated response is accepted only with a complete next-key/next-upload-id marker pair.
• A fallback marker is synthesized only when both markers are absent and the final upload provides a safe advancing pair.
• Partial marker pairs, empty unsafe fallbacks, cycles, and stalled pagination are rejected.
• HTTP 401/403 is classified as authentication failure before any service-code handling.
• Idempotence requires HTTP 404 plus the exact structured NoSuchUpload code; generic 404s and message substrings are not treated as success.
• Exact-key CLI filtering prevents a nonconforming server response from widening cleanup to similarly prefixed objects.

Compatibility and migration

BREAKING contract process: this PR updates protected command-reference documentation and extends the output-v3 schema introduced by #266. It does not modify schemas/output_v1.json or schemas/output_v2.json, and it does not change their runtime contracts. Multipart commands added here explicitly emit v3 envelopes.

The dependency chain is main -> #272 -> #266 -> #269; the command-launcher fix remains isolated in #272 and the output-v3 foundation remains isolated in #266.

Validation

Static restack checks:

• stable multipart patch-id preserved: 16de49fa3049b3cb05161b00c66232e06af1178f
• range-diff shows only removal of the obsolete local main.rs launcher hunk
• no crates/cli/src/main.rs delta relative to the feat(rc-output): introduce output schema v3 #266 base
• no changes to output v1/v2 schemas
• git diff --check passes

Final isolated gates in /tmp/rc-target-1366-final with CARGO_INCREMENTAL=0 and CARGO_BUILD_JOBS=1:

• cargo fmt --all --check
• cargo clippy --workspace -- -D warnings
• cargo test --workspace
• cargo test -p rustfs-cli --test multipart_incomplete (9 passed)
• cargo test -p rustfs-cli --test output_schema_v3 (6 passed)
• INSTA_UPDATE=no cargo test -p rustfs-cli --features golden --test golden (5 passed)
• jq empty for all schemas and JSON fixtures
• protected-files check with the required BREAKING marker

All local checks pass.

Final review resolution (2026-07-21)

• Corrected service-error precedence so a structured NotImplemented response remains UnsupportedFeature even when RustFS returns HTTP 404.
• Kept authentication first and exact 404 NoSuchUpload abort idempotence ahead of generic classification.
• Added focused list/abort regression tests for the mixed HTTP-status/service-code responses.
• Re-ran cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings, cargo test --workspace, multipart (9 passed), output-v3 (6 passed), and golden (5 passed) gates in /tmp/rc-target-1366-rereview; all pass.