Merge #572/#575: native browse paging/lease/pacing, differential equal-refusal + budget isolation

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

# Conflicts:
#	docs/drivers/AbCip.md

docs/drivers/AbCip.md

@@ -78,7 +78,7 @@ the driver's `DriverConfig` JSON. Key fields:
 - **`Tags`** — pre-declared `AbCipTagDefinition` list; `Members` for UDT fan-out, `SafetyTag` for GuardLogix safety-partition tags.
 - **`Probe`** — connectivity-probe `Enabled` / `Interval` / `Timeout` / `ProbeTagPath`.
 - **`Transport`** — absent (default ⇒ `Native`), `Native`, or `Libplctag` (fallback); see [Transport](#transport-transport-option).
-- **Discovery** — `EnableControllerBrowse` (`@tags` walk) and `EnableDeclarationOnlyUdtGrouping` (whole-UDT read fast path).
+- **Discovery** — `EnableControllerBrowse` (`@tags` walk), `EnableDeclarationOnlyUdtGrouping` (whole-UDT read fast path) and `browsePageDelayMs` (native browse pacing, see [Native browse](#native-browse-paging-pacing-and-template-leases)).
 - **Alarms** — `EnableAlarmProjection` + `AlarmPollInterval` for the ALMD projection.
 
 Full per-field descriptions live in `AbCipDriverOptions.cs`. The JSON skeleton is
@@ -209,8 +209,11 @@ The driver has two interchangeable wire transports, selected by one `DriverConfi
 - ⚠️ RESIDUAL (#567): wide-struct **fragmented writes** (8-byte alignment) are unit-tested only. Production
   presses are read-only and there is no bench controller, so this cannot be proven; it stays open until a
   bench controller exists.
-- Native browse: listing pages are unpaced, and template reads outside an enumeration open a connection per
-  call (#572).
+- Native browse (#572, resolved in code): listing paging no longer assumes ascending instance order, pages
+  are paced, and a browse's template reads share one lease. One residual: whether a real controller ever
+  lists a page out of order is unobserved — the reader is now correct either way. `browsePageDelayMs` is
+  not editable in the AdminUI form (its typed model drops unknown keys on save, #576); author it in the
+  driver-config JSON.
 - Micro800, routed and `logixpccc` paths are covered by `ab_server` only. The Micro800 profile passes
   natively. The AbLegacy default excludes `logixpccc` (and PLC-5).
 - Follow-up issues for this workstream: #564 to #577.
@@ -255,6 +258,27 @@ integration fixture is down during normal dev (Docker host fixture currently off
 See [Uns.md §Array tags](../Uns.md#array-tags-1-d) for the cross-driver coverage matrix
 and the UI authoring flow.
 
+## Native browse: paging, pacing and template leases
+
+Native symbol browse (`transport` = `Native`; libplctag pages inside its own library and is unaffected):
+
+- **Paging continues past the highest instance seen**, not the last entry of a page. The Symbol Object
+  listing is requested from `start`; the next request starts at `max(instance in the reply) + 1`, so the
+  order a controller lists a page in does not matter. A "more" reply whose highest instance is still below
+  its `start` (or equals `uint.MaxValue`) made no progress and fails with `BadReply` ("made no progress")
+  rather than looping against the controller.
+- **Pages are paced.** `browsePageDelayMs` (driver config, default **5**, `0` = back-to-back, negative =
+  `0`) pauses before every page after the first. 5 ms is small against a page's own round-trip, so a
+  50k-symbol browse gains a few seconds, but it breaks the back-to-back burst (one request in flight, roughly
+  a Studio 5000 online browse) into slices the controller's message processing can interleave with. Raise it
+  for a controller that is tight on CPU; the pause applies per listing (the controller listing and each
+  program listing).
+- **Template reads in a browse share one lease.** `DiscoverAsync` reads the UDT templates (and nested
+  templates) of a device through a single batch reader (`IAbCipTemplateReaderFactory.CreateBatch`); the
+  native batch reader holds one device lease from its first read until the browse of that device ends,
+  instead of leasing per template. `FetchUdtShapeAsync` outside a discovery run is unchanged: one
+  self-contained lease per call.
+
 ## Controller-discovered UDT member variables
 
 When `EnableControllerBrowse` is set, the driver walks the controller's `@tags` symbol table and