build: make verify-fork-functions honor 'diverged' mode like its sibling

verify-fork-versions.sh reads the 4th column of fork-upstream-map.toml
and skips the content check for forks marked 'diverged', with a WARN.
verify-fork-functions.sh had no notion of mode and hard-failed every
fork, so kernel (30), bootloader (5) and installer (2) blocked every
canonical build for drift the map itself records as accepted, with
comments saying a full rebase is later work.

Both verifiers now read the same source of truth. Diverged forks are
reported and counted as warnings; every other fork still gates. This
turned a 5-fork / 43-function hard failure into 2 real findings, which
are fixed in the accompanying relibc and base commits.

local/scripts/verify-fork-functions.sh

@@ -64,6 +64,7 @@ if [[ ${#TARGET_FORKS[@]} -eq 0 ]]; then
 fi
 
 VIOLATIONS=0
+DIVERGED_WARNINGS=0
 TOTAL_MISSING=0
 
 for fork in "${TARGET_FORKS[@]}"; do
@@ -78,6 +79,15 @@ for fork in "${TARGET_FORKS[@]}"; do
         continue
     fi
 
+    # Mode from the authoritative map (4th column), same source of truth as
+    # verify-fork-versions.sh. A fork marked 'diverged' has substantial
+    # post-fork work and is deliberately behind upstream master -- the map
+    # records for each one that a full rebase is later work. Its sibling
+    # verifier skips the content check for those forks with a WARN; this one
+    # used to hard-fail them, so kernel/bootloader/installer blocked every
+    # build for drift the project has already accepted. Report, do not gate.
+    fork_mode=$(awk -v f="$fork" '$1==f {print $4}' "$PROJECT_ROOT/local/fork-upstream-map.toml" 2>/dev/null | head -1)
+
     # Determine upstream branch
     upstream_branch="master"
     if ! (cd "$fork_dir" && git rev-parse --verify upstream/master >/dev/null 2>&1); then
@@ -215,7 +225,14 @@ for fork in "${TARGET_FORKS[@]}"; do
             echo "  This likely means a bad merge or cherry-pick dropped them silently."
             echo "  Fix: ./local/scripts/upgrade-forks.sh $fork"
         fi
-        VIOLATIONS=$((VIOLATIONS + 1))
+        if [[ "$fork_mode" == "diverged" ]]; then
+            echo "  NOTE: $fork is 'diverged' in local/fork-upstream-map.toml —"
+            echo "        reported as a warning, not a build gate. Rebasing it is"
+            echo "        tracked work; see local/docs/FORK-BUMP-PATCHING-POLICY.md."
+            DIVERGED_WARNINGS=$((DIVERGED_WARNINGS + 1))
+        else
+            VIOLATIONS=$((VIOLATIONS + 1))
+        fi
     elif [[ "$QUIET" -eq 0 ]]; then
         echo -e "\033[1;32mOK: $fork — all upstream functions present\033[0m"
     fi
@@ -227,5 +244,8 @@ if [[ "$VIOLATIONS" -gt 0 ]]; then
     exit 1
 fi
 
-echo -e "\033[1;32mAll forks retain all upstream functions.\033[0m"
+if [[ "${DIVERGED_WARNINGS:-0}" -gt 0 ]]; then
+    echo -e "\033[1;33m$DIVERGED_WARNINGS diverged fork(s) are behind upstream (warning only).\033[0m"
+fi
+echo -e "\033[1;32mAll gated forks retain all upstream functions.\033[0m"
 exit 0