docs(embed): a configuration walkthrough for the VA Report Designer

Replaces the two-sentence section with the steps a report author needs:
where the URL goes, that the parameter has to be bound into the object's
query or VA never sends it, and how to tell a working mapping from a broken
one when the report runs. Also drops the note about intnx argument names,
which was explaining a decision rather than the behaviour.

docs/embed-va.md

@@ -143,9 +143,6 @@ Notes:
 - a transform only applies to date and datetime columns; on any other column the parameter is ignored and the warning banner says so
 - the offset is a whole number; unknown anchors, periods and operations are rejected with a warning naming the entry
 
-!!! note
-    The anchor names describe the resulting date rather than mirroring SAS `intnx` arguments.  The arithmetic runs in the browser, so a URL that reads like an `intnx` call would not always behave like one.
-
 ## Filter Modes
 
 When running in `embed=va` mode, the editor provides two filter modes, controlled by the **Auto-apply** checkbox:
@@ -157,7 +154,30 @@ A status indicator shows whether a filter change is pending, loading, or idle.
 
 ## Configuration in VA
 
-In the VA Report Designer, add a **Data-Driven Content** object and set the URL to the editor route shown above.  Be sure that any report level filters have their corresponding parameters added to the DDC object itself.
+The mapping lives entirely in the URL of the report object, so the job is to get the right URL onto a **Data-driven content** object and make sure the parameters it names actually reach it.
+
+1. **Add the object.**  In the VA Report Designer, insert a **Data-Driven Content** object, or select the one already on the page.
+
+2. **Point it at Data Controller.**  Open **Options** on the right and paste the SAS Job Execution URL of your DC deployment into **Web Content URL**, with `embed=va` and one `va_parmap` entry per parameter:
+
+    ```text
+    https://yourserver/SASJobExecution/?_file=/YOUR/APPLOC/services/DC.html#/editor/YOURLIB.YOURTABLE?embed=va&va_parmap=REGION_TAB1-REGION
+    ```
+
+    Everything before the `#` is the normal deployment URL; the `#/editor/...` part is the DC route, and `?embed=va` plus the `va_parmap` entries are what this page describes.  One object per report tab, each with its own entry, is what lets two tabs filter the same column differently.
+
+3. **Make the parameter reach the object.**  VA sends an object only the parameters its query uses.  A report parameter that the object's data does not reference never arrives, and the mapping then has nothing to map - DC reports it as `VA is not sending ...` in the banner.  So bind the parameter into the object (assign it as a source on the object's query, as you would for any other visual), rather than only defining it at report level.
+
+4. **Save the report**, then open it.  DC shows the applied filter above the grid, so a correct mapping is visible without opening the editor:
+
+    ```text
+    FILTER : ( ( REGION = 'Europe' ) )
+    ```
+
+    Something wrong shows the banner instead, with the cause and the fix - see [When a mapping cannot be used](#when-a-mapping-cannot-be-used) above.
+
+!!! note
+    The URL is read when the object loads, so a change to `va_parmap` takes effect when the report (or the page holding the object) is next opened.
 
 ## Debugging