feat(sprint3): §4.1/4.3/4.4 — JSONL logging, disk alert, runbook

§4.1 — Structured JSONL log (Invoke-CIJob.ps1)
  Each job now emits a parallel invoke-ci.jsonl alongside the transcript.
  Write-JobEvent appends one JSON line per phase transition (ts, jobId,
  phase, status, data). Events emitted at: job.start, phase1.clone-repo
  start/success, phase2-3b.vm-start start/success, phase4.wait-ready
  start/success, phase5.build start/success, phase6.artifacts start/success,
  job.success/failure (with elapsedSec and error string).
  Silent no-op if $jsonLog is null (log dir setup failed). Errors in
  Write-JobEvent are swallowed — logging never breaks the build.
  Enables post-hoc per-phase duration analysis with jq or ConvertFrom-Json.

§4.3 — Disk space alert (scripts/Watch-DiskSpace.ps1)
  Checks drive free space every 15 min (scheduled by Register-CIScheduledTasks).
  Below MinFreeGB (default 50 GB): writes Warning to Windows Application Event Log
  (source CI-DiskAlert, EventId 1001) and exits 1 so Task Scheduler flags the run.
  Optional -WebhookUrl for Discord/Gitea webhook notification.
  Register-CIScheduledTasks.ps1 updated with Task 3: CI-DiskSpaceAlert (every 15 min).

§4.4 — Incident runbook (docs/RUNBOOK.md)
  Four scenarios with symptom / triage commands / fix / escalation:
    1. Runner offline in Gitea UI
    2. All builds fail in Phase 2 (clone/start/IP)
    3. Builds are slow (per-phase JSONL analysis, disk/CPU/NAT checks)
    4. Template VMX corrupt after host crash (lock removal + backup restore)
  Quick-reference table at the end.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/Invoke-CIJob.ps1

@@ -159,14 +159,16 @@ $jobArtifactDir = Join-Path $ArtifactBaseDir $JobId
 $hostCloneDir   = Join-Path $env:TEMP "ci-src-$JobId"
 $cloneVmxPath   = $null
 $leaseFile      = $null   # §2.1 IP lease file path — released in finally
+$jsonLog        = $null   # §4.1 JSONL structured log path
 $startTime      = Get-Date
 
-# ── Start transcript ──────────────────────────────────────────────────────────
+# ── Start transcript + JSONL log ──────────────────────────────────────────────
 $transcriptStarted = $false
 try {
     $jobLogDir = Join-Path $LogDir $JobId
     if (-not (Test-Path $jobLogDir)) { New-Item -ItemType Directory -Path $jobLogDir -Force | Out-Null }
     $transcriptPath = Join-Path $jobLogDir 'invoke-ci.log'
+    $jsonLog        = Join-Path $jobLogDir 'invoke-ci.jsonl'
     # -Append allows starting a new transcript even when VS Code (or another host)
     # has already opened a transcript on this PowerShell session.
     Start-Transcript -Path $transcriptPath -Append -Force -ErrorAction Stop
@@ -176,6 +178,29 @@ catch {
     Write-Warning "[Invoke-CIJob] Could not start transcript: $_"
 }
 
+# ── §4.1 Structured event emitter ────────────────────────────────────────────
+# Appends a single JSON line to invoke-ci.jsonl per phase transition.
+# Silent no-op if $jsonLog is null (transcript setup failed).
+function Write-JobEvent {
+    param(
+        [Parameter(Mandatory)] [string] $Phase,
+        [Parameter(Mandatory)] [string] $Status,   # start | success | failure | info
+        [hashtable] $Data = @{}
+    )
+    if (-not $script:jsonLog) { return }
+    $event = [ordered]@{
+        ts     = (Get-Date -Format 'o')
+        jobId  = $script:JobId
+        phase  = $Phase
+        status = $Status
+        data   = $Data
+    }
+    try {
+        $event | ConvertTo-Json -Compress -Depth 5 |
+            Add-Content -Path $script:jsonLog -Encoding UTF8 -ErrorAction Stop
+    } catch { }  # never let logging break the build
+}
+
 Write-Host "============================================================"
 Write-Host "[Invoke-CIJob] Job          : $JobId"
 Write-Host "[Invoke-CIJob] Repository   : $RepoUrl"
@@ -187,6 +212,14 @@ Write-Host "[Invoke-CIJob] Artifacts    : $jobArtifactDir"
 Write-Host "[Invoke-CIJob] Started      : $startTime"
 Write-Host "============================================================"
 
+Write-JobEvent -Phase 'job' -Status 'start' -Data @{
+    repo     = $RepoUrl
+    branch   = $Branch
+    commit   = $Commit
+    template = $TemplatePath
+    snapshot = $SnapshotName
+}
+
 $exitCode = 0
 
 try {
@@ -195,6 +228,7 @@ try {
     # still cloned here and copied via WinRM zip to avoid injecting a PAT
     # into the VM environment.
     Write-Host "`n[Phase 1/6] Cloning repository on host..."
+    Write-JobEvent -Phase 'phase1.clone-repo' -Status 'start'
     if (Test-Path $hostCloneDir) { Remove-Item $hostCloneDir -Recurse -Force }
     $gitArgs = @('clone', '--depth', '1', '--branch', $Branch)
     if ($Submodules) { $gitArgs += '--recurse-submodules' }
@@ -224,6 +258,7 @@ try {
         }
     }
     Write-Host "[Invoke-CIJob] Source cloned to: $hostCloneDir"
+    Write-JobEvent -Phase 'phase1.clone-repo' -Status 'success' -Data @{ dir = $hostCloneDir }
 
     # ── Phase 2-3b: Clone + Start + IP (serialized via file-based mutex) ────
     # §2.1: With capacity:4 and DHCP on VMnet8, concurrent vmrun starts can race
@@ -237,6 +272,7 @@ try {
     if (-not (Test-Path $leasesDir)) { New-Item -ItemType Directory -Path $leasesDir -Force | Out-Null }
 
     Write-Host "`n[Phase 2/6] Acquiring VM-start lock (prevents DHCP collision with capacity>1)..."
+    Write-JobEvent -Phase 'phase2-3b.vm-start' -Status 'start'
     $lockStream   = $null
     $lockDeadline = (Get-Date).AddMinutes(10)
     while ($true) {
@@ -296,6 +332,7 @@ try {
         }
         [System.IO.File]::WriteAllText($leaseFile, $JobId)
         Write-Host "[Invoke-CIJob] IP $VMIPAddress leased for job $JobId."
+        Write-JobEvent -Phase 'phase2-3b.vm-start' -Status 'success' -Data @{ ip = $VMIPAddress; vmx = $cloneVmxPath }
 
     } finally {
         # Release lock — next waiting job can now enter clone→start→IP phase
@@ -310,13 +347,16 @@ try {
 
     # ── Phase 4: Wait for readiness ───────────────────────────────────────
     Write-Host "`n[Phase 4/6] Waiting for VM readiness..."
+    Write-JobEvent -Phase 'phase4.wait-ready' -Status 'start' -Data @{ ip = $VMIPAddress }
     & "$scriptDir\Wait-VMReady.ps1" `
         -VMPath    $cloneVmxPath `
         -IPAddress $VMIPAddress `
         -VmrunPath $VmrunPath
+    Write-JobEvent -Phase 'phase4.wait-ready' -Status 'success'
 
     # ── Phase 5: Remote build (copy source + build inside VM) ─────────────
     Write-Host "`n[Phase 5/6] Invoking remote build..."
+    Write-JobEvent -Phase 'phase5.build' -Status 'start'
     $remoteBuildParams = @{
         IPAddress     = $VMIPAddress
         Credential    = $credential
@@ -326,9 +366,11 @@ try {
     if ($BuildCommand -ne '')        { $remoteBuildParams['BuildCommand']        = $BuildCommand }
     if ($GuestArtifactSource -ne '') { $remoteBuildParams['GuestArtifactSource'] = $GuestArtifactSource }
     & "$scriptDir\Invoke-RemoteBuild.ps1" @remoteBuildParams
+    Write-JobEvent -Phase 'phase5.build' -Status 'success'
 
     # ── Phase 6: Collect artifacts ────────────────────────────────────────
     Write-Host "`n[Phase 6/6] Collecting artifacts..."
+    Write-JobEvent -Phase 'phase6.artifacts' -Status 'start'
     & "$scriptDir\Get-BuildArtifacts.ps1" `
         -IPAddress         $VMIPAddress `
         -Credential        $credential `
@@ -337,6 +379,8 @@ try {
         -IncludeLogs
 
     $elapsed = (Get-Date) - $startTime
+    Write-JobEvent -Phase 'phase6.artifacts' -Status 'success' -Data @{ dir = $jobArtifactDir }
+    Write-JobEvent -Phase 'job' -Status 'success' -Data @{ elapsedSec = [int]$elapsed.TotalSeconds }
     Write-Host "`n============================================================"
     Write-Host "[Invoke-CIJob] SUCCESS — Job $JobId completed in $($elapsed.ToString('mm\:ss'))"
     Write-Host "[Invoke-CIJob] Artifacts: $jobArtifactDir"
@@ -345,6 +389,10 @@ try {
 catch {
     $exitCode = 1
     $elapsed  = (Get-Date) - $startTime
+    Write-JobEvent -Phase 'job' -Status 'failure' -Data @{
+        elapsedSec = [int]$elapsed.TotalSeconds
+        error      = "$_"
+    }
     Write-Host "`n============================================================"
     Write-Host "[Invoke-CIJob] FAILURE — Job $JobId failed after $($elapsed.ToString('mm\:ss'))"
     Write-Host "Error: $_"