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Task 5.1: Delete runner/Install-Runner.ps1 (superseded by Setup-Host.ps1).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/Watch-RunnerHealth.ps1

@@ -127,7 +127,7 @@ if ($recentCount -ge $MaxRestarts) {
                 "Check Event Viewer → Application (source: $logSource) and F:\CI\act_runner\logs\."
     Write-Warning "[RunnerHealth] $limitMsg"
     Write-CIEvent -EventId 1004 -EntryType Error -Message $limitMsg
-    Send-Webhook -Content ":sos: **CI Runner Alert** — $limitMsg"
+    Send-Webhook -Content "[ALERT] CI Runner Alert -- $limitMsg"
     exit 1
 }
 
@@ -147,8 +147,8 @@ try {
     $evtType = if ($newStatus -eq 'Running') { 'Information' } else { 'Warning' }
     Write-CIEvent -EventId 1003 -EntryType $evtType -Message $restartMsg
 
-    $icon = if ($newStatus -eq 'Running') { ':warning:' } else { ':sos:' }
-    Send-Webhook -Content "$icon **CI Runner Alert** — $restartMsg"
+    $prefix = if ($newStatus -eq 'Running') { '[WARNING]' } else { '[ALERT]' }
+    Send-Webhook -Content "$prefix CI Runner Alert -- $restartMsg"
 
     exit $(if ($newStatus -eq 'Running') { 0 } else { 1 })
 }
@@ -156,6 +156,6 @@ catch {
     $errMsg = "$ServiceName restart failed: $_"
     Write-Warning "[RunnerHealth] $errMsg"
     Write-CIEvent -EventId 1004 -EntryType Error -Message $errMsg
-    Send-Webhook -Content ":sos: **CI Runner Alert** — $errMsg"
+    Send-Webhook -Content "[ALERT] CI Runner Alert -- $errMsg"
     exit 1
 }