Merge R2-11 TagConfig consolidation (arch-review round 2) [PR #434]

Findings 01/C-1, 01/P-1 (single TagConfigIntent.Parse in Commons, 4 copies
delegate, parse-once) + 05 CONV-2/UNDER-1/UNDER-6 (shared strict TagConfigJson
readers, per-driver Inspect() + writable key, FOCAS capability pre-flight,
Modbus probe timeoutMs, deploy-gate Warn|Error). Phase C runtime-strict flip
deferred. T22/T24 deferred. Auto-merged AddressSpaceApplier.cs + DriverHostActor.cs
with R2-04/R2-10; verified OpcUaServer.Tests 286/286 + Runtime.Tests 396/396.
Build clean.

docs/Uns.md

@@ -231,6 +231,53 @@ Combined with historization (values are arrays — history of the whole array sn
 
 See the individual driver docs under `docs/drivers/` for per-driver implementation details.
 
+## Writable equipment tags (`writable` key)
+
+An equipment tag is **writable by default** — the materialised OPC UA node is created
+`CurrentReadWrite` and inbound client writes are routed to the device (subject to the
+`WriteOperate` LDAP role gate). Setting the optional `"writable": false` key in a tag's
+`TagConfig` makes the node **read-only** at the driver seam. The six typed tag editors
+(Modbus, S7, AB CIP, AB Legacy, TwinCAT, FOCAS) expose this as a **Writable** checkbox
+(checked by default); it can also be hand-authored in the raw-JSON textarea.
+
+| Condition | Node |
+|---|---|
+| `writable` absent | Writable (driver default) — existing configs are unchanged |
+| `writable: false` | Read-only |
+| `writable: true` | Writable |
+
+The key is honoured by Modbus, S7, AB CIP, AB Legacy, and TwinCAT. **FOCAS forces
+read-only regardless** — FOCAS PMC writes are unsupported in the wire client, so its
+editor shows the checkbox disabled/unchecked and any authored `writable:true` is ignored
+(and flagged at the deploy gate below). Node-level authz (LDAP `WriteOperate`) remains the
+effective write gate above this flag.
+
+## Deploy-time TagConfig validation (`Deployment:TagConfigValidationMode`)
+
+The deploy gate inspects every equipment tag's `TagConfig` per its bound driver type and
+surfaces **strictness warnings** — a present-but-invalid enum value (e.g. a typo'd
+`dataType`, which the lenient runtime silently defaults to the wrong width with `Good`
+status), a structurally-unparseable TagConfig, or (FOCAS) an authored `writable:true`.
+
+The behaviour is controlled by `Deployment:TagConfigValidationMode` in `appsettings.json`:
+
+| Mode | Behaviour |
+|---|---|
+| `Warn` (default) | Non-blocking: warnings are logged and appended to the deployment result message; the deploy still succeeds. Existing configs never break. |
+| `Error` | Blocking: warnings fold into the draft-gate reject list — a config with a typo'd enum (or unparseable TagConfig) cannot be re-deployed until fixed. Opt-in per environment once the fleet deploys warning-clean. |
+
+Running servers are untouched either way — the gate only sees re-deploys. Unmapped drivers
+(Galaxy, OpcUaClient) are skipped. **Unknown keys are never warned on**: the `TagConfig`
+blob is a shared namespace (platform intent keys coexist with per-driver address keys and
+forward-compat keys the typed editors preserve), so there is no single schema to validate
+against — parsers read known fields and ignore the rest by design.
+
+> **Note (runtime strictness is deferred).** In this release the runtime parsers stay
+> *lenient* (a typo'd enum still silently defaults) — only the deploy gate reports it.
+> Flipping the runtime parsers to strict (a typo'd enum ⇒ `BadNodeIdUnknown` instead of a
+> wrong-width `Good`) is a deliberate future phase, to be taken only after fleets have run
+> `Error` mode clean. Tracked in `archreview/plans/STATUS.md`.
+
 ## Galaxy address picker — native-alarm pre-fill
 
 When the Galaxy address picker selects an attribute that is itself an alarm

docs/drivers/FOCAS.md

@@ -15,6 +15,16 @@ OtOpcUa is **read-only** against FOCAS; all reads go over the native wire
 protocol using the documented command IDs. Writes return
 `BadNotWritable` by design.
 
+> **Equipment tags are forced read-only (R2-11, migration note).** The equipment-tag parser
+> (`FocasEquipmentTagParser`) now hard-codes `Writable: false` regardless of any authored
+> `"writable": true` — previously such a tag advertised a writable node whose write always failed at
+> the wire with `BadNotWritable`; now it fails one step earlier at the driver seam (same family of Bad
+> status, no successful operation changes). The AdminUI FOCAS editor shows the Writable checkbox
+> disabled/unchecked, and the deploy gate warns when a config requests `writable:true`. Additionally,
+> equipment-tag references now run the same capability-matrix pre-flight authored tags get: a reference
+> whose address violates the device series' matrix fails to resolve (`BadNodeIdUnknown`) instead of
+> reaching the wire. Honour `writable` here once PMC writes ship in the wire client.
+
 > **PDU version (v3 / FANUC 30i/31i).** The wire client **accepts inbound PDU versions `{1, 3}`**
 > (`FocasWireProtocol`) while still emitting v1 on requests. Older controls + the docker mock answer
 > v1; modern controls (Makino Pro 5 / FANUC **31i-B**) answer v3. **Validated live against a real