ci: call the org leak-scan workflow

.github/leak-scan-allowlist.json

@@ -0,0 +1,28 @@
+{
+  "allow": [
+    {
+      "rule": "machine-path",
+      "path": "README.md",
+      "match": "/home/joe",
+      "reason": "The rule table documents the two account paths this rule catches; a doc that cannot name them documents nothing."
+    },
+    {
+      "rule": "private-project",
+      "path": "README.md",
+      "match": "driftless",
+      "reason": "Explains why the lookahead ends the repo name instead of using a word boundary; the explanation needs the sibling name it once missed."
+    },
+    {
+      "rule": "workspace-convention",
+      "path": "README.md",
+      "match": "_active/",
+      "reason": "The rule table names the monorepo conventions this rule catches; same self-documentation exemption as machine-path."
+    },
+    {
+      "rule": "workspace-convention",
+      "path": "README.md",
+      "match": ".data/plans",
+      "reason": "The allowlist example must show a realistic match string, and a fake one would teach the wrong format."
+    }
+  ]
+}

.github/workflows/leak-scan-self.yml

@@ -0,0 +1,11 @@
+# This repo is public too, so it holds itself to the rule it enforces elsewhere.
+# The filename differs from leak-scan.yml because that name is taken here by the
+# reusable workflow this one calls.
+name: leak-scan
+on:
+  pull_request:
+  push:
+    branches: [main]
+jobs:
+  leak-scan:
+    uses: Back-Road-Creative/.github/.github/workflows/leak-scan.yml@main