docs(scripting): document {{equip}} equipment-relative tag paths

CLAUDE.md

@@ -170,4 +170,4 @@ runtime publish gate uses, so what the editor accepts/rejects matches publish
 exactly. The backend lives in
 `src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ScriptAnalysis/` (six minimal-API
 endpoints under `/api/script-analysis/*`, gated by the `FleetAdmin` policy).
-See `docs/ScriptEditor.md` for the full guide.
+See `docs/ScriptEditor.md` for the full guide. Scripts may use the `{{equip}}` token for equipment-relative tag paths that resolve per-equipment at deploy time — see the "Equipment-relative tag paths" section in `docs/ScriptEditor.md`.

docs/ScriptEditor.md

@@ -293,6 +293,83 @@ Register the replacement in `EndpointRouteBuilderExtensions.AddAdminUI`
 
 ---
 
+## Equipment-relative tag paths (`{{equip}}`)
+
+### Why
+
+Today each VirtualTag bound to a script typically needs its own near-duplicate
+script because tag paths are hard-coded absolutes (e.g. `TestMachine_001.Speed`).
+The `{{equip}}` token breaks this coupling: point many VirtualTags' `ScriptId` at
+a single template script, and each resolves the token to its own equipment's tag
+base prefix at deploy time. No schema change is required — sharing a `Script`
+record across VirtualTags already works; `{{equip}}` is what makes the shared
+script resolve per-equipment.
+
+### Before / after
+
+**Before — one script per machine:**
+
+```csharp
+// Script "Calc_TestMachine_001" — hard-coded, cannot reuse
+return ctx.GetTag("TestMachine_001.Speed").Value;
+```
+
+**After — one shared template:**
+
+```csharp
+// Script "Calc_Speed" — works for any machine
+return ctx.GetTag("{{equip}}.Speed").Value;
+```
+
+`TestMachine_001` and `TestMachine_002` both bind `ScriptId = "Calc_Speed"`.
+At deploy, each VirtualTag receives its own expanded copy:
+`TestMachine_001.Speed` and `TestMachine_002.Speed` respectively.
+
+### Token rules
+
+- The token is `{{equip}}` (double braces, lowercase).
+- It is substituted **only inside `ctx.GetTag(…)` / `ctx.SetVirtualTag(…)` first-argument
+  string literals** — comments, logger strings, and other code are untouched.
+- The operator writes the separator and tail: `ctx.GetTag("{{equip}}.Speed")`,
+  `ctx.GetTag("{{equip}}.Sub.Field")`, etc.
+- The token expands to the equipment's **tag base prefix** — the common
+  substring-before-the-first-dot of that equipment's configured driver-tag
+  `FullName` values. Example: tags `TestMachine_001.Speed` and
+  `TestMachine_001.Temp` → base `TestMachine_001`.
+
+### Validation requirement
+
+Saving a VirtualTag that is bound to a `{{equip}}`-using script is rejected in
+the AdminUI if the equipment does not have at least one configured driver tag, or
+if its tags span multiple object prefixes (i.e. the common prefix is ambiguous or
+absent). The rejection message is surfaced as a clear validation error on the save
+form. This check is enforced eagerly so that an unresolved `{{equip}}` token —
+which would leave a path that resolves to nothing at runtime (Bad quality) — can
+never reach the deployed artifact.
+
+### Editor support
+
+In the Monaco script editor (ScriptEdit page and the `/uns` virtual-tag modal's
+inline script panel):
+
+- **Hover** — hovering a `{{equip}}` path literal shows an
+  *"Equipment-relative path — resolved at deploy"* note.
+- **Completions** — typing `{{equip}}.` inside a `GetTag`/`SetVirtualTag` literal
+  offers completion of attribute leaf names (the part after the first dot of known
+  tag references in the catalog).
+
+### Maintainer note
+
+Substitution runs at the two compose seams —
+`Phase7Composer.Compose` and `DeploymentArtifact.BuildEquipmentVirtualTagPlans`
+— via the shared `ZB.MOM.WW.OtOpcUa.Commons.Types.EquipmentScriptPaths` helper,
+**before** dependency extraction. The runtime, the static change-trigger
+dependency graph, and the literal-only path rule are therefore all unchanged:
+by the time they see the script, `{{equip}}` has been replaced with a concrete
+tag-base prefix and the path is a normal string literal.
+
+---
+
 ## Known Limitations / Follow-ups
 
 - **Tag-path completion shows resolvable keys only.** Surfacing the UNS browse