chore(#3813): delete the caller-less listMilestoneArchiveDirs seam; #1883 contract now pins the live path (#4029)

* test(#3813): pin the #1883 unreadable-milestones contract on the live planning-snapshot path

* fix(#3813): delete the caller-less listMilestoneArchiveDirs seam; #1883 contract now pins the live path

* chore(#3813): changeset fragment (pr number backfilled after PR creation)

* chore(#3813): backfill changeset PR number (4029)

* chore(#3813): docs-exempt marker — internal dead-code removal

---------

Co-authored-by: sim <sim@local>

scripts/lint-test-file-count.allowlist.json

@@ -129,6 +129,7 @@
     },
     "verify": {
       "files": [
+        "verify-archive-dirs-live-path.test.cjs",
         "verify-health.test.cjs",
         "verify-mvp-uat.test.cjs",
         "verify-npm-publish.test.cjs",
@@ -136,7 +137,7 @@
         "verify-work-auto-transition.test.cjs",
         "verify.test.cjs"
       ],
-      "issue": "3767",
+      "issue": "#3813 \u2014 the live-path #1883 suite drives buildPlanningSnapshot in-process with an fs fault; the verify module suites are CLI-driving and cannot host an fs monkeypatch",
       "justification": "verify-command-grounding added by #2401/#3678; allowlist follow-up landed with #3606 (base was red on this lane)."
     },
     "install": {