feat(sprint5): quality pass, smoke test workflow, Get-CIJobSummary

Task 5.1: Delete runner/Install-Runner.ps1 (superseded by Setup-Host.ps1).
Task 5.2: Replace Unicode/Discord emoji in Watch-DiskSpace.ps1, Watch-RunnerHealth.ps1,
          Test-E2E-Section3.3.ps1 with plain-text prefixes ([WARNING], [ALERT], [WARN]).
Task 5.3: docs/TEST-PLAN-v1.3-to-HEAD.md: ForEach-Object -Parallel replaced with Start-Job;
          -RepositoryUrl replaced with -RepoUrl (3 occurrences); PS7 syntax removed.
Task 5.4: scripts/Get-CIJobSummary.ps1 (new): scans JSONL logs in F:\CI\Logs, prints summary
          table per job, -JobId detail view, -Failed filter, -Last N.
Task 3.5: gitea/workflows/self-test.yml (new): workflow_dispatch, smoke-windows + smoke-linux.
          scripts/Test-Smoke.ps1 (new): invokes Invoke-CIJob.ps1 with marker-file build,
          asserts artifact dir and JSONL success event.
Task 5.6: docs/BEST-PRACTICES.md Section 10 added: SHA256 pinning policy, priority table,
          PS 5.1 implementation pattern, update guidance.

scripts/Test-E2E-Section3.3.ps1

@@ -198,7 +198,7 @@ if ($baselineResult -and $guestCloneResult) {
             Write-Host "✓ §3.3 guest-clone is FASTER by $(Format-Elapsed ([TimeSpan]::FromSeconds($diff)))" -ForegroundColor Green
         }
         else {
-            Write-Host "⚠ Host-side is faster by $(Format-Elapsed ([TimeSpan]::FromSeconds(-$diff)))" -ForegroundColor Yellow
+            Write-Host "[WARN] Host-side is faster by $(Format-Elapsed ([TimeSpan]::FromSeconds(-$diff)))" -ForegroundColor Yellow
         }
     }
     else {