fix(tests): populate help-parameter vars in BeforeDiscovery so the param-help check runs

The 'help parameter help' Context in Help.tests.ps1 uses -Foreach $helpParameterNames,
but $helpParameterNames was assigned only in BeforeAll (run phase). Pester evaluates
-Foreach during DISCOVERY, so the collection was $null then and the Context expanded
to ZERO tests -- the 'no stale/extra parameters documented in help' check has been a
silent no-op in this template and every module scaffolded from it.

Fix: also populate $helpParameters/$helpParameterNames in BeforeDiscovery (mirroring
$commandParameters, which already works in that same block), so the Context generates
one test per documented parameter.

Verified locally with Pester 5.7.1: a -Foreach collection set in BeforeDiscovery
generates tests; the same collection set only in BeforeAll generates zero.

Flagged by Copilot on the ReScenePS test-scaffolding-alignment PR (#18).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tablackburn

tests/Help.tests.ps1

@@ -111,11 +111,15 @@ BeforeAll {
 Describe "Test help for <_.Name>" -ForEach $commands {
 
     BeforeDiscovery {
-        # Get command help, parameters, and links
+        # Get command help, parameters, and links. These are duplicated in BeforeAll
+        # below; they must also exist here because the nested Context blocks use them in
+        # -ForEach, which Pester evaluates during discovery (before BeforeAll runs).
         $command               = $_
         $commandHelp           = Get-Help -Name $command.Name -ErrorAction 'SilentlyContinue'
         $commandParameters     = global:FilterOutCommonParameters -Parameters $command.ParameterSets.Parameters
         $commandParameterNames = $commandParameters.Name
+        $helpParameters        = global:FilterOutCommonParameters -Parameters $commandHelp.Parameters.Parameter
+        $helpParameterNames    = $helpParameters.Name
         $helpLinks             = $commandHelp.relatedLinks.navigationLink.uri | Where-Object { $_ -match '^https?://' }
     }