feat(persistence): PostgreSQL assistant store, chat persist fixes, gateway scripts

- Add SQLAlchemy Core repos, pg adapter/compat, assistant_store factory, Alembic bootstrap and migration/cutover scripts.

- Harden chat_message writes (NUL scrub for PG), turn_uuid on attempt failure, WS turn_runner fallbacks and gateway executed_turn_uuid init.

- start_gateway: log paths, PS7 stderr handling via cmd, background stdout/stderr redirect; runtime assistant_runtime_log_dir export.

- Ops: clear_all_chat_sessions with PG-only --postgresql and env-gated wipe; clear_postgres_chat_sessions.ps1.

- Tests: SA repos, pg compat, persist fallback, smoke env isolation; CI and docs touch-ups.

Co-authored-by: Cursor <cursoragent@cursor.com>

runtime/operations/scripts/clear_postgres_chat_sessions.ps1

@@ -0,0 +1,71 @@
+# Wipe all chat_session rows (and related session-bound rows) on PostgreSQL only.
+# Loads _local/system.env into the process, forces PG backend, sets confirmation env.
+# Usage (from repo root is fine):
+#   .\runtime\operations\scripts\clear_postgres_chat_sessions.ps1
+# Dry-run (count only):
+#   .\runtime\operations\scripts\clear_postgres_chat_sessions.ps1 -DryRun
+
+param(
+    [switch]$DryRun = $false
+)
+
+$ErrorActionPreference = "Stop"
+
+function Import-DotEnvFile([string]$path) {
+    if (-not (Test-Path $path)) { return }
+    Get-Content -LiteralPath $path -Encoding UTF8 | ForEach-Object {
+        $line = $_.Trim()
+        if (-not $line -or $line.StartsWith("#")) { return }
+        $idx = $line.IndexOf("=")
+        if ($idx -lt 1) { return }
+        $k = $line.Substring(0, $idx).Trim()
+        $v = $line.Substring($idx + 1).Trim()
+        if ($k) {
+            [System.Environment]::SetEnvironmentVariable($k, $v, "Process")
+        }
+    }
+}
+
+$repoRoot = $null
+$cur = (Resolve-Path $PSScriptRoot).Path
+for ($i = 0; $i -lt 16; $i++) {
+    if (Test-Path (Join-Path $cur "oclaw.json")) {
+        $repoRoot = $cur
+        break
+    }
+    $parent = Split-Path -Parent $cur
+    if (-not $parent -or $parent -eq $cur) { break }
+    $cur = $parent
+}
+if (-not $repoRoot) {
+    throw "Could not find oclaw.json above $PSScriptRoot"
+}
+Set-Location $repoRoot
+$env:PYTHONPATH = $repoRoot
+
+$envFile = Join-Path $repoRoot "_local\system.env"
+Import-DotEnvFile $envFile
+
+$env:AIA_ASSISTANT_DB_BACKEND = "postgresql"
+$env:AIA_CONFIRM_CHAT_SESSION_WIPE = "1"
+
+$venvPython = Join-Path $repoRoot ".venv\Scripts\python.exe"
+$pythonExe = $(if (Test-Path $venvPython) { $venvPython } else { "python" })
+
+$args = @(
+    (Join-Path $repoRoot "runtime\operations\scripts\clear_all_chat_sessions.py")
+)
+if ($DryRun) {
+    $args += "--dry-run"
+} else {
+    $args += "--yes"
+}
+$args += "--postgresql"
+
+Write-Host "repo=$repoRoot" -ForegroundColor Cyan
+Write-Host "env_file=$envFile" -ForegroundColor DarkGray
+Write-Host "python=$pythonExe" -ForegroundColor DarkGray
+Write-Host "dry_run=$DryRun" -ForegroundColor DarkGray
+
+& $pythonExe @args
+exit $LASTEXITCODE