refactor(replication): move resyncer pure decision logic into rustfs-replication (M2) (#6180)

* refactor(replication): move resyncer pure decision logic into rustfs-replication (M2)

Pure-move milestone M2 of the ECStore replication split (backlog#1675
P1-17): relocate the resyncer's IO-free decision helpers, with their unit
tests, into the crates they already belong to by type ownership. No
behavior change.

Moved into crates/replication:
- resync.rs: resync_status_duration
- delete.rs: resync_existing_delete_replication_info,
  replicate_delete_outcome, target_delete_version_id,
  delete_marker_purge_version_id, delete_marker_purge_mrf_entry
- object.rs: version_identity_drifted, is_replication_target_offline_error,
  SsecPassthroughCapability, SsecPassthroughGate, ssec_passthrough_gate,
  ssec_passthrough_evidence_present (param-demoted to the echoed
  customer-algorithm string; ECStore keeps the HeadObjectOutput adapter)
- filemeta.rs: NULL_VERSION_ID wire literal (crate-owned copy per the
  filemeta-independence contract)

ECStore rewiring (Rule #14: imports stay in *_boundary.rs):
- resync/object-decision/target boundaries re-export the moved symbols;
  resyncer call sites are unchanged
- bucket_target_sys keeps only the verdict cache + TTL and re-exports the
  capability enum so existing consumer paths keep compiling

Not moved (signatures carry ECStore or aws-sdk types):
verify_resync_head_result, resync_target_error_detail, the SdkError
classifiers, the replicate_all_* option/info builders, and the env-coupled
bounded_resync_max_jobs admission clamp. README milestone table updated.

* chore(replication): retire the datatypes.rs relay early

README sanctions retiring datatypes.rs ahead of M4. The module was a
pure relay (resync boundary -> datatypes -> mod.rs facade) with no
external consumer importing it directly, so the facade now re-exports
ResyncStatusType from replication_resync_boundary and the relay file is
deleted. Consumers stay behind the ECStore facade, keeping Migration
Rule #15 intact — the original retirement wording ("consumers import
through rustfs-replication directly") conflicted with that rule and is
corrected in the README.

* chore(arch): extend migration guards to the M2-moved decision contracts

The adversarial review of the M2 move found the per-symbol ratchet in
check_architecture_migration_rules.sh was not extended for the moved
symbols, leaving them free to be redefined in ECStore or imported past
their boundary without CI noticing:

- resync definition pin + boundary fences gain resync_status_duration;
- the object-decision boundary fences gain the five delete-family
  helpers (delete_marker_purge_mrf_entry, delete_marker_purge_version_id,
  replicate_delete_outcome, resync_existing_delete_replication_info,
  target_delete_version_id);
- the target-boundary fence gains the SSE-C gate family, the offline
  classifier, and version_identity_drifted;
- a new definition pin rejects ECStore redefinitions of the M2-moved
  fns/enums (ssec_passthrough_evidence_present deliberately excluded:
  ECStore keeps a thin HeadObjectOutput adapter under that name).

Mutation-verified: a probe fn ssec_passthrough_gate under
crates/ecstore/src/bucket/replication trips the new pin.

Also anchors the intentionally-duplicated NULL_VERSION_ID wire literal
from the filemeta side and tightens the M2 README note on
bounded_resync_max_jobs.

crates/filemeta/src/fileinfo.rs

@@ -42,6 +42,9 @@ const FILEINFO_PART_BITMAP_WORD_BITS: usize = std::mem::size_of::<u64>() * 8;
 const FILEINFO_PART_BITMAP_WORDS: usize = MAX_FILEINFO_PARTS.div_ceil(FILEINFO_PART_BITMAP_WORD_BITS);
 
 // Additional constants from Go version
+// Intentionally duplicated (S3 wire literal): rustfs-replication and
+// rustfs-object-data-cache carry their own independent "null" constants so
+// they stay free of a rustfs-filemeta dependency. Keep all three in sync.
 pub const NULL_VERSION_ID: &str = "null";
 // pub const RUSTFS_ERASURE_UPGRADED: &str = "x-rustfs-internal-erasure-upgraded";