feat: persist compact session state

shared/hooks/scripts/Show-SessionStatePointer.ps1

@@ -0,0 +1,4 @@
+[CmdletBinding()]
+param()
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+if (Test-Path (Join-Path $root '.ai-session/state.json')) { Write-Output 'Task state is available in .ai-session/state.json; read it only if needed.' }