test(coverage): run the Pester suite with code coverage

tests/Invoke-Coverage.ps1 runs the suite with Pester's profiler-based
coverage collector and writes both JaCoCo XML and a coverage-summary.json
in the same shape vitest and jest emit, so one reader handles every tool
in the fleet.

CodeCoverage.Path is every *.ps1 in the repo root, including the ones no
test touches. They report 0% and drag the total down, which is correct -
measuring only the already-tested files answers "how well covered is the
covered code". The same mistake in vitest form had evo.www reporting 93%.

Baseline: 222 tests pass, 7.0% of commands (219/3,125 across 24 scripts).
Pester counts commands, not statements; the collector labels it as such
rather than filing it under a unit it is not.

.gitignore

@@ -16,3 +16,6 @@ desktop.ini
 
 # Internal working notes (superseded by TOKEN_SAVINGS.md)
 md/
+
+# Pester coverage output (regenerated; never committed)
+coverage/

tests/Invoke-Coverage.ps1

@@ -0,0 +1,91 @@
+# Evomedia.net Token Savers — https://github.com/evomedia-net/evo.zscripts
+# Created by Kelly Michels · dev@evomedia.net
+# Licensed under the MIT License. See LICENSE.
+
+# Invoke-Coverage.ps1 — run the Pester suite with code coverage.
+#
+#   .\tests\Invoke-Coverage.ps1            run everything, print the summary
+#   .\tests\Invoke-Coverage.ps1 -Quiet     just the numbers (for tooling)
+#
+# Writes coverage/ :
+#   pester-coverage.xml     JaCoCo, for anything that reads a standard format
+#   coverage-summary.json   the same shape vitest/jest emit, so the fleet
+#                           coverage collector reads all three identically
+#
+# WHY EVERY SCRIPT IS MEASURED, NOT JUST THE TESTED ONES
+# ------------------------------------------------------
+# CodeCoverage.Path covers every top-level *.ps1, including the ones no test
+# touches. They report 0% and drag the total down, which is correct: the
+# alternative measures only the files that already have tests and answers "how
+# well covered is the covered code" - a question nobody is asking. The same
+# mistake in vitest form made www look 91% covered when it was 17%.
+#
+# Pester counts *commands*, not statements. The collector labels it accordingly;
+# the two are not interchangeable and averaging them would be nonsense.
+
+[CmdletBinding(PositionalBinding = $false)]
+param([switch]$Quiet)
+
+$ErrorActionPreference = "Stop"
+
+$RepoRoot = Split-Path -Parent $PSScriptRoot
+$OutDir   = Join-Path $RepoRoot "coverage"
+$Jacoco   = Join-Path $OutDir "pester-coverage.xml"
+$Summary  = Join-Path $OutDir "coverage-summary.json"
+
+Import-Module Pester -MinimumVersion 5.0 -ErrorAction Stop
+
+# Every script in the repo root. ZKiller/ZKillOnly and friends are included
+# deliberately - see the header.
+$targets = @(Get-ChildItem -Path $RepoRoot -Filter "*.ps1" -File | Select-Object -ExpandProperty FullName)
+if (-not $targets) { Write-Error "No *.ps1 found in $RepoRoot"; exit 1 }
+
+if (Test-Path $OutDir) { Remove-Item $OutDir -Recurse -Force }
+New-Item -ItemType Directory -Force -Path $OutDir | Out-Null
+
+$cfg = New-PesterConfiguration
+$cfg.Run.Path                     = Join-Path $RepoRoot "tests"
+$cfg.Run.PassThru                 = $true
+$cfg.Output.Verbosity             = if ($Quiet) { "None" } else { "Normal" }
+$cfg.CodeCoverage.Enabled         = $true
+$cfg.CodeCoverage.Path            = $targets
+$cfg.CodeCoverage.OutputFormat    = "JaCoCo"
+$cfg.CodeCoverage.OutputPath      = $Jacoco
+$cfg.CodeCoverage.UseBreakpoints  = $false   # the profiler-based collector; far faster
+$cfg.Should.ErrorAction           = "Continue"
+
+$r = Invoke-Pester -Configuration $cfg
+
+$analyzed = [int]$r.CodeCoverage.CommandsAnalyzedCount
+$executed = [int]$r.CodeCoverage.CommandsExecutedCount
+$pct      = if ($analyzed -gt 0) { [math]::Round(($executed / $analyzed) * 100, 2) } else { 0 }
+
+# Same shape as vitest/jest json-summary. "statements" is Pester's command
+# count; the key is reused so one reader handles every tool, and the unit is
+# named in the collector rather than pretended away here.
+$json = [ordered]@{
+    total = [ordered]@{
+        statements = [ordered]@{ pct = $pct; covered = $executed; total = $analyzed }
+    }
+    tests = [ordered]@{
+        passed  = [int]$r.PassedCount
+        failed  = [int]$r.FailedCount
+        skipped = [int]$r.SkippedCount
+        total   = [int]$r.TotalCount
+    }
+    unit  = "commands"
+} | ConvertTo-Json -Depth 6
+
+# WriteAllText, not Set-Content: Set-Content -Encoding utf8 on 5.1 writes a BOM,
+# and a BOM makes python's json.load throw on the first character.
+[IO.File]::WriteAllText($Summary, $json, (New-Object Text.UTF8Encoding $false))
+
+if (-not $Quiet) {
+    Write-Host ""
+    Write-Host "Coverage: $pct%  ($executed/$analyzed commands across $($targets.Count) scripts)" -ForegroundColor Cyan
+    Write-Host "  $Jacoco"
+    Write-Host "  $Summary"
+    Write-Host ""
+}
+
+exit $(if ($r.FailedCount -gt 0) { 1 } else { 0 })