fix(#2766): scan archived phases and read table-shaped Gaps/deferred entries (#3082)

* fix(#2766): scan archived phases and read table-shaped Gaps/deferred entries

Three silent false negatives in cmdAuditUat and its readers, all failing in
the reassuring (false-negative) direction — a UAT audit whose entire job is
to catch leftover work reporting zero over real work:

1. Archived phases invisible (src/uat.cts cmdAuditUat): on milestone
   completion milestone.cts MOVES phase dirs into
   .planning/milestones/<version>-phases/ (archive-by-default since #1871),
   leaving .planning/phases/ empty or absent. Partial archive → false
   all-clear; full archive → hard error indistinguishable from a broken
   install. Fix: enumerate archived dirs via the canonical
   getArchivedPhaseDirs seam (phase-locator.cts); archived dirs deliberately
   bypass getMilestonePhaseFilter (which scopes to the CURRENT milestone —
   applying it to past-milestone dirs would discard every one and reinstate
   the bug).

2. Table-shaped deferred-items.md yielded zero items (splitGapsEntries
   keyed on bullet openers only; a GFM table row starts with |). Fix: union
   of bullet + numbered + table-row splits.

3. Table-shaped ## Gaps yielded zero items (same bullet-only splitter).
   Fix: same union walker.

The table walker is deliberately NOT routed through parseMarkdownTable
(ADR-2143 §3 — that reads only the first table and treats ragged/headerless
shapes as errors, the wrong contract for a hand-written backstop table
that must surface its rows). New additive archived_milestone field labels
provenance.

Fix authored by issue reporter gavin-ray and verified against the published
tarball; maintainer triage (trek-e) confirmed all three findings. Cherry-
picked onto fresh next after prior PR #2832 closed for staleness; re-verified
under gsd-test + reviews. 21 regression tests including the negative
direction (bullet-only unchanged, status: resolved still suppressed, empty
phases dir still succeeds).

* chore(#2766): backfill changeset PR number 3082

---------

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

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

@@ -1,5 +1,5 @@
 {
-  "_doc": "Baseline of modules currently exceeding the 2-test-file limit. Each entry locks in TODAY's exact test filenames as the allowlisted set (identity ratchet). Adding a NEW test file to a capped module fails (novel). Removing one requires pruning this list (stale, ratchet-down). When a cluster drops to ≤ 2, remove its entry entirely. New entries require justification in PR description.",
+  "_doc": "Baseline of modules currently exceeding the 2-test-file limit. Each entry locks in TODAY's exact test filenames as the allowlisted set (identity ratchet). Adding a NEW test file to a capped module fails (novel). Removing one requires pruning this list (stale, ratchet-down). When a cluster drops to \u2264 2, remove its entry entirely. New entries require justification in PR description.",
   "modules": {
     "config": {
       "files": [
@@ -125,6 +125,14 @@
         "prompt-budget.test.cjs"
       ],
       "issue": "2929"
+    },
+    "audit": {
+      "files": [
+        "audit-command-cutover.test.cjs",
+        "audit-fix-command.test.cjs",
+        "fix-2766-audit-uat-archived-and-table-shapes.test.cjs"
+      ],
+      "issue": "2766"
     }
   }
 }