test(e2e): large-object degraded-read EOF truncation regression net (dist-13) (#4709)

Adds an S3-API-level e2e regression net proving that a large-object GET on a
degraded EC set never returns a silently truncated body under a full
Content-Length -- the historical "unexpected EOF" bug fixed on main by
rustfs#4594 (short-body GetObject stream -> UnexpectedEof), rustfs#4560
(in-place per-part legacy degradation for the lazy multipart reader), and
rustfs#4585 (DARE package-boundary truncation detection). Those fixes each
ship a *unit* regression; this covers the layer they do not -- the full HTTP
GET path streaming a real body reconstructed from real on-disk EC shards.

New file crates/e2e_test/src/degraded_read_eof_regression_test.rs, single-node
4-disk (EC 2+2) DiskFaultHarness, three scenarios:

  (a) one disk offline: a 6 MiB single object (>=2 EC stripes) and a 3x5 MiB
      multipart object GET back byte-identical with the correct Content-Length.
  (b) mid-stream bitrot within quorum: 2 of 4 shards corrupted mid-file on a
      large multipart object still reconstructs the full, hash-matching body.
  (c) beyond read quorum (the heart of the net): 3 of 4 shards corrupted
      mid-file -- the read MUST fail cleanly (non-2xx or a mid-stream body
      error), NEVER close with a truncated body under the full Content-Length.

The shared get_checked() helper panics on the forbidden outcome (a clean 2xx
whose collected body is shorter than the advertised Content-Length), so the
truncation bug can never be silently tolerated.

CI placement: these spawn a 4-disk server per test and are resource-heavy, so
they stay OUT of the fast PR e2e-smoke filter. A new e2e-reliability nextest
test-group (max-threads=1) serializes them (and the existing
reliability_disk_fault_test) across nextest's process boundary; ci-7's nightly
full-e2e run picks them up. Visible via `cargo nextest list -p e2e_test`.

Refs rustfs/backlog#1150 (dist-13), rustfs/backlog#1155, rustfs#4594,
rustfs#4560, rustfs#4585, rustfs#2955.

.config/nextest.toml

@@ -31,11 +31,27 @@
 [test-groups]
 ecstore-serial-flaky = { max-threads = 1 }
 
+# Reliability / fault-injection e2e tests each spawn a single-node 4-disk RustFS
+# server and manipulate its disk directories at runtime (crates/e2e_test:
+# reliability_disk_fault_test, degraded_read_eof_regression_test / dist-13). They
+# are correct in isolation but resource-heavy; serialize them under nextest's
+# process boundary (serial_test's #[serial] does not cross it) so several 4-disk
+# servers never run at once. ci-7's nightly picks these up via the e2e suite;
+# they are deliberately NOT in the fast PR `e2e-smoke` filter.
+e2e-reliability = { max-threads = 1 }
+
 # --- default profile (local): serialize the flaky groups, never retry --------
 [[profile.default.overrides]]
 filter = 'package(rustfs-ecstore) & (test(concurrent_resend_same_part_commits_one_generation) | test(/^store::bucket::tests::bucket_delete_(mark_delete_marks|purge_removes|default_s3_delete)/))'
 test-group = 'ecstore-serial-flaky'
 
+# Serialize the 4-disk reliability / degraded-read e2e tests (see the
+# e2e-reliability test-group note above). The matching ci-profile override is at
+# the end of the file, after [profile.ci] is declared.
+[[profile.default.overrides]]
+filter = 'package(e2e_test) & test(/^(reliability_disk_fault|degraded_read_eof_regression)_test::/)'
+test-group = 'e2e-reliability'
+
 # ---------------------------------------------------------------------------
 # ci profile — the strict CI gate (ci.yml `cargo nextest run --profile ci`)
 # ---------------------------------------------------------------------------
@@ -85,6 +101,14 @@ retries = 2
 filter = 'package(rustfs-ecstore) & test(walk_dir_does_not_charge_consumer_backpressure_to_the_stall_budget)'
 retries = 2
 
+# Serialize the 4-disk reliability / degraded-read e2e tests under the ci
+# profile too (see the e2e-reliability test-group note near the top). Not a
+# quarantine: no retries, just single-threaded so several 4-disk servers never
+# run concurrently when ci-7's nightly runs the full e2e suite.
+[[profile.ci.overrides]]
+filter = 'package(e2e_test) & test(/^(reliability_disk_fault|degraded_read_eof_regression)_test::/)'
+test-group = 'e2e-reliability'
+
 # ---------------------------------------------------------------------------
 # e2e-smoke profile — PR smoke subset of the e2e_test crate (backlog#1149 ci-4)
 # ---------------------------------------------------------------------------