feat: persist compact session state

shared/hooks/scripts/Record-Compact.ps1

@@ -0,0 +1,7 @@
+[CmdletBinding()]
+param()
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+$stateDir = Join-Path $root '.ai-session'
+New-Item $stateDir -ItemType Directory -Force | Out-Null
+('{"event":"compact","timestamp":"' + (Get-Date).ToUniversalTime().ToString('o') + '"}') | Add-Content (Join-Path $stateDir 'telemetry.jsonl')
+exit 0