ci: adopt estate CI standard — thin caller + wp-framework PHPUnit + 300-line split

- ci.yml: thin caller → peptide-e2e reusable (tests: wp-framework, has_js: true, line_limit_paths: inc)
- deploy.yml: retire standalone validate; gate deploy on ci.yml via workflow_call
- composer.json: test script → vendor/bin/phpunit (explicit)
- inc/helpers.php: split 311→211 lines; nav walker extracted to nav-walker.php
- inc/nav-walker.php: new — Peptide_Starter_Nav_Walker + menu fallback (123 lines)
- functions.php: require nav-walker.php before helpers.php; version 2.2.2→2.3.0
- style.css: version header 2.2.2→2.3.0
- package.json / package-lock.json: minimal npm manifest for lint-js job

Agent-Session: claude/adopt-ci-20260616

package-lock.json

@@ -0,0 +1,13 @@
+{
+  "name": "peptide-starter-theme",
+  "version": "2.3.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "peptide-starter-theme",
+      "version": "2.3.0",
+      "license": "GPL-2.0-or-later"
+    }
+  }
+}