fix(agentsmd-audit): scope secrets-scanner placeholder allowlist to matched token

validate-secrets.sh checked the placeholder allowlist regex against the
whole line before running any secret-pattern regex. An unrelated
placeholder-looking token anywhere on the line (e.g. "example" or
"your-token-here" in a trailing comment) suppressed detection of a real
credential earlier on the same line. Scope the allowlist check to the
matched secret-candidate substring only, which the per-match re-check
already did downstream but the whole-line pre-check short-circuited
before it ever ran.

Extend validate-secrets.bats with a case proving a real AWS-style key is
still caught when a placeholder token sits elsewhere on the line.
Regenerate the flat-mirror copy at
plugins/core/skills/agentsmd-audit/scripts/validate-secrets.sh via
scripts/sync-plugin-content.sh --all per ADR-0016.

plugins/core/.apm/skills/agentsmd-audit/scripts/validate-secrets.sh

@@ -87,14 +87,14 @@ for fpath in find_agents_md(repo_root):
     with open(fpath, encoding="utf-8", errors="replace") as f:
         lines = f.readlines()
     for i, line in enumerate(lines, start=1):
-        if PLACEHOLDER_RE.search(line):
-            continue
         for label, pattern in PATTERNS:
             m = pattern.search(line)
             if not m:
                 continue
-            # Re-check placeholder allowlist against just the matched value, in case
-            # the placeholder marker sits outside the regex's own match span.
+            # Scope the placeholder allowlist to the matched secret-candidate
+            # substring only. Checking the whole line would let an unrelated
+            # placeholder-looking token elsewhere on the line (e.g. in a
+            # trailing comment) suppress detection of a real credential.
             value = m.group(0)
             if PLACEHOLDER_RE.search(value):
                 continue

plugins/core/.apm/skills/agentsmd-audit/tests/validate-secrets.bats

@@ -52,6 +52,19 @@ EOF
     assert_output --partial "connection string"
 }
 
+@test "still catches a real secret when a placeholder token sits elsewhere on the same line" {
+    cat > "$TMPDIR/AGENTS.md" <<'EOF'
+# AGENTS.md
+
+## Setup
+- AWS_ACCESS_KEY_ID=AKIAABCDEFGHIJKLMNOP # see your-token-here for an example, gitleaks:allow (synthetic fixture — this test verifies the placeholder allowlist is scoped to the matched value, not the whole line)
+EOF
+    run bash "$SCRIPT" "$TMPDIR"
+    assert_failure
+    assert_output --partial "AWS access key ID"
+    assert_output --partial "AGENTS.md:4"
+}
+
 @test "detects secrets in a nested AGENTS.md, not just root" {
     mkdir -p "$TMPDIR/packages/api"
     cat > "$TMPDIR/AGENTS.md" <<'EOF'

plugins/core/skills/agentsmd-audit/scripts/validate-secrets.sh

@@ -87,14 +87,14 @@ for fpath in find_agents_md(repo_root):
     with open(fpath, encoding="utf-8", errors="replace") as f:
         lines = f.readlines()
     for i, line in enumerate(lines, start=1):
-        if PLACEHOLDER_RE.search(line):
-            continue
         for label, pattern in PATTERNS:
             m = pattern.search(line)
             if not m:
                 continue
-            # Re-check placeholder allowlist against just the matched value, in case
-            # the placeholder marker sits outside the regex's own match span.
+            # Scope the placeholder allowlist to the matched secret-candidate
+            # substring only. Checking the whole line would let an unrelated
+            # placeholder-looking token elsewhere on the line (e.g. in a
+            # trailing comment) suppress detection of a real credential.
             value = m.group(0)
             if PLACEHOLDER_RE.search(value):
                 continue