feat: expose runtime workload owner snapshots (#3607)

docs/architecture/migration-progress.md

@@ -5,18 +5,19 @@ Status values: `[ ]` not started, `[~]` in progress, `[x]` complete, `[!]` block
 ## Current Context
 
 - Issue: [`rustfs/backlog#660`](https://github.com/rustfs/backlog/issues/660)
-- Branch: `overtrue/arch-scanner-replication-admission-snapshots`
-- Baseline: `origin/main` after `rustfs/rustfs#3605`
-  (`00ca3b7c1c4ffbe98c0dd8530cb26b63e94c586a`).
+- Branch: `overtrue/arch-foreground-scanner-admission-snapshots`
+- Baseline: `origin/main` after `rustfs/rustfs#3606`
+  (`7cb7aefc3bfd33cfaa46c718db15f00b0471fe88`).
 - PR type for this branch: `consumer-migration`
 - Runtime behavior changes: none.
-- Rust code changes: extend read-only workload admission snapshots from heal
-  repair counters to replication runtime worker and queue counters.
+- Rust code changes: extend the RustFS workload admission registry from
+  repair/replication snapshots to foreground-read, scanner, and metadata owner
+  snapshots.
 - CI/script changes: extend migration guard coverage for RustFS workload
   admission provider implementations.
-- Docs changes: add RustFS replication provider notes to
+- Docs changes: add RustFS runtime owner provider notes to
   [`workload-admission-contracts.md`](workload-admission-contracts.md) and
-  record the API-058/R-018 provider slice.
+  record the API-059/R-019 provider slice.
 
 ## Phase 0 Tasks
 
@@ -198,6 +199,21 @@ Status values: `[ ]` not started, `[~]` in progress, `[x]` complete, `[!]` block
     check, migration and layer guards, formatting, diff hygiene, risk scan, and
     three-expert review.
 
+- [x] `API-059/R-019` Expose RustFS runtime owner admission snapshots.
+  - Completed slice: extend the RustFS workload admission provider to map
+    foreground-read disk permit state, scanner active work units, and bucket
+    metadata runtime initialization into the workload registry.
+  - Acceptance: RustFS-level workload admission snapshots expose existing
+    foreground-read, scanner, and metadata owner state without changing
+    admission, queueing, scanner scheduling, metadata loading, metadata locks,
+    or object write behavior.
+  - Must preserve: disk-read semaphore acquisition, scanner cycle scheduling,
+    bucket metadata initialization and loading, object write paths, request
+    guards, and queue behavior.
+  - Verification: focused workload admission tests, focused RustFS library
+    check, migration and layer guards, formatting, diff hygiene, risk scan, and
+    three-expert review.
+
 - [x] `TEST-PRTYPE-001` Check PR type enum consistency.
   - Acceptance: `./scripts/check_architecture_migration_rules.sh` parses the
     allowed PR types from [`crate-boundaries.md`](crate-boundaries.md) and fails

docs/architecture/workload-admission-contracts.md

@@ -92,3 +92,23 @@ snapshot from the existing replication pool and queue statistics:
 This is an observation surface only. Replication admission, queue channel
 capacity, worker resize behavior, MRF handling, target dispatch, and resync
 behavior are unchanged.
+
+## RustFS Runtime Owner Snapshot Extraction
+
+The RustFS integration layer now extends the workload admission registry with
+additional read-only owner mappings:
+
+- `ForegroundRead` reuses the storage `ConcurrencyManager` disk-read permit
+  snapshot so the RustFS-level provider exposes the same active and limit
+  counts as the storage-local provider.
+- `Scanner` reports the existing scanner active work-unit counter. When the
+  counter is zero, the snapshot remains `Unknown` because the current counter
+  cannot distinguish an idle scanner from a scanner that has not initialized.
+- `Metadata` reports `Open` once the bucket metadata runtime handle is
+  available, and `Unknown` before initialization.
+- `ForegroundWrite` remains `Unknown` until a write-specific admission owner
+  exposes a read-only surface.
+
+This is an observation surface only. Disk-read permit acquisition, scanner
+cycle scheduling, bucket metadata loading, metadata locks, object write paths,
+and queue behavior are unchanged.