chore(hygiene): root secret-capture guards — .gitignore patterns + opt-in pre-commit secret scan (plan R2-08 T3)

tools/hooks/README.md

@@ -0,0 +1,5 @@
+# Git hooks
+
+`pre-commit` scans the staged diff for obvious credential material (inbound API tokens `sbk_...`, plaintext password assignments in root `.txt`/`.md` additions) and blocks the commit if found (bypass a false positive with `git commit --no-verify`).
+
+Opt in once with: `git config core.hooksPath tools/hooks`

tools/hooks/pre-commit

@@ -0,0 +1,22 @@
+#!/bin/sh
+# Root secret-capture guard (arch-review 08 round 2 NF1).
+# Scans ONLY the staged diff for obvious credential material and blocks the
+# commit if found. Opt-in: `git config core.hooksPath tools/hooks`.
+# Bypass a knowing false positive with: git commit --no-verify
+
+diff=$(git diff --cached -U0)
+
+# 1) Inbound API token: sbk_<hex>_<token>
+token=$(printf '%s\n' "$diff" | grep -nE '^\+.*sbk_[0-9a-f]{16,}_[A-Za-z0-9_-]{20,}')
+
+# 2) Plaintext password assignment added to a root-level .txt/.md file.
+pw=$(printf '%s\n' "$diff" | grep -nE '^\+.*[Pp]assword[0-9]*[[:space:]]*[:=][[:space:]]*[^[:space:]]')
+
+if [ -n "$token" ] || [ -n "$pw" ]; then
+	echo "pre-commit: possible secret in staged changes — commit blocked." >&2
+	[ -n "$token" ] && echo "  inbound API token (sbk_...) matched:" >&2 && printf '%s\n' "$token" >&2
+	[ -n "$pw" ] && echo "  plaintext password assignment matched:" >&2 && printf '%s\n' "$pw" >&2
+	echo "Bypass a false positive with: git commit --no-verify" >&2
+	exit 1
+fi
+exit 0