docs(humanizer): v5.1.0 release notes across plugin + marketplace docs

- Plugin README: add "What's New in v5.1.0" section with humanizer overview,
  before/after example, plain-language vocabulary table, --raw flag docs.
  Bump version badge 5.0.0 → 5.1.0. Add Version History row.
- Plugin CLAUDE.md: add humanizer.mjs + humanizer-data.mjs to Scanner Lib
  table. Add "Plain-Language Output (v5.1.0)" section documenting output
  modes, vocabularies, and Wave 5 lessons. Bump test count 635 → 792 across
  52 test files.
- Marketplace root README: bump config-audit entry 5.0.0 → 5.1.0, update
  one-line description to mention plain-language UX, add bullet for the
  v5.1.0 humanizer, bump test count 635+ → 792+.

Test-normalizer hardening (consequence of growing CLAUDE.md):
walkClaudeMdCascade walks upward from the marketplace-medium fixture into
this plugin's own CLAUDE.md, so any docs edit ripples into
`scanners[*].activeConfig.claudeMdEstimatedTokens`. The v5.0.0 byte-stability
contract is about scanner internals being unchanged, not ancestor input
content being frozen. Normalizers in json-backcompat, raw-backcompat,
posture-humanizer, scan-orchestrator-humanizer, and snapshot-default-output
now strip claudeMdEstimatedTokens to <ANCESTOR_DERIVED>. The
default-output snapshot for scan-orchestrator was re-seeded via
UPDATE_SNAPSHOT=1 (intent: Wave 6 docs additions; humanizer prose
unchanged).

Verify:
- grep -E "5\.1\.0|v5\.1\.0" README.md CLAUDE.md ../../README.md | wc -l = 12
- node --test 'tests/**/*.test.mjs' = 792/792 pass
- self-audit configGrade A (97), pluginGrade A (100), readmeCheck.passed true

plugins/config-audit/tests/scanners/posture-humanizer.test.mjs

@@ -16,7 +16,10 @@ const POSTURE_STDERR_SNAPSHOT = resolve(REPO, 'tests/snapshots/v5.0.0-stderr/pos
 
 /**
  * Normalize a runPosture result for snapshot comparison by zeroing out
- * time-varying fields and machine-specific paths.
+ * time-varying fields, machine-specific paths, and ancestor-cascade-derived
+ * counts. `claudeMdEstimatedTokens` reflects walkClaudeMdCascade walking
+ * upward from the fixture; any docs edit to this plugin's own CLAUDE.md
+ * ripples into it even though scanner behavior is unchanged.
  */
 function normalizePosture(p) {
   const out = JSON.parse(JSON.stringify(p));
@@ -28,6 +31,9 @@ function normalizePosture(p) {
     if (Array.isArray(out.scannerEnvelope.scanners)) {
       for (const s of out.scannerEnvelope.scanners) {
         s.duration_ms = 0;
+        if (s.activeConfig && 'claudeMdEstimatedTokens' in s.activeConfig) {
+          s.activeConfig.claudeMdEstimatedTokens = '<ANCESTOR_DERIVED>';
+        }
       }
     }
   }