feat(rul,cml): durability findings — config lost after compaction (v5.5.0 / A)

Per the official "what survives compaction" model (context-window.md):
only the project-root CLAUDE.md (+ unscoped rules) is re-injected after a
context compaction. Two additive, structural findings (low severity):

- RUL: a large (>50-line) PATH-SCOPED rule — reloads only on a matching
  file read, and is not re-injected after compaction, so must-hold rules
  can silently drop mid-session.
- CML: a NESTED (subdirectory) CLAUDE.md — not re-injected after
  compaction (only the project root is).

Additive (no new scanner, count stays 13); one humanizer entry each;
hermetic temp-fixture tests (positive + negative). Suite 957 -> 961,
SC-5 byte-stable, self-audit A/A.

Known limitation (pre-existing, broader than A): the lightweight
frontmatter parser reads inline `paths:` but not YAML block sequences,
so block-sequence-scoped rules are still seen as unscoped. Deferred.

Part of v5.5.0 "steering-model I". Foundation (active-config-reader
enumeration) deferred to v5.6 with B.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ter3E2JSi1Khgmuf2kady8

scanners/rules-validator.mjs

@@ -122,6 +122,23 @@ export async function scan(targetPath, discovery) {
       }));
     }
 
+    // A large PATH-SCOPED rule follows best practice, but path-scoped rules are
+    // NOT re-injected after a context compaction — they reload only when a
+    // matching file is read again (context-window.md). A big one carrying
+    // must-always-hold instructions can silently drop out mid-session.
+    if (frontmatter?.paths && lines > 50) {
+      findings.push(finding({
+        scanner: SCANNER,
+        severity: SEVERITY.low,
+        title: 'Large path-scoped rule is lost after compaction',
+        description: `${file.relPath} is path-scoped (${lines} lines). Path-scoped rules load only when a matching file is read, and after a context compaction they are not re-injected until a matching file is read again — so a large scoped rule carrying must-always-hold instructions can silently drop out mid-session.`,
+        file: file.absPath,
+        evidence: `${lines} lines, path-scoped`,
+        recommendation: 'If parts of this rule must always apply, move them to the project-root CLAUDE.md (re-injected after compaction). Keep path-scoped rules for context only needed when those files are open.',
+        autoFixable: false,
+      }));
+    }
+
     // Check file extension
     if (!file.absPath.endsWith('.md')) {
       findings.push(finding({