fix(framework): track anchor presence separately from value (T51 WP0b rework)

${VAR:-} collapsed exported-empty into genuinely-unset, mis-filing
both-empty and the two mixed empty/unset states as informational where
the charter requires WARNs. Presence now tracked via [[ -v VAR ]]
alongside value: NOTES only when both variables are genuinely absent;
any present-but-empty or single-present state emits a loud WARN per
missing/empty anchor, each naming the launchers as authority (unset and
empty get distinct wording). Suite: the wrong both-empty note arm
replaced by three warn arms (both-empty, host-empty+brain-unset,
host-unset+brain-empty); warn arms accept >=1 warn with zero notes
(single-present states warn once, both-present-empty warns twice — per
anchor, by design); red control now mutates presence tracking back to
the nonemptiness collapse (the reviewed defect shape) and must emit
NOTEs for both-empty. 10 arms green; gates green.

packages/mosaic/framework/tools/_scripts/test-structure-anchor-check.sh

@@ -9,7 +9,7 @@
 #   1. both present+nonempty      -> pass ([OK]), no warns, no notes
 #   2a. host missing, brain set   -> warn naming MOSAIC_HOST_ROOT + launchers
 #   2b. brain missing, host set   -> warn naming MOSAIC_BRAIN_HOME + launchers
-#   2c. present-but-EMPTY counts as missing (both empty -> state 3; one empty -> state 2)
+#   2c. present-but-EMPTY counts as missing (warns; NEVER informational)
 #   3. neither present            -> informational notes, NON-AUTHORITATIVE, never warn
 # Arms include genuinely-UNSET (env -u) forms, not only empty strings.
 # Red control: empty-vs-unset distinction removed in a mutated copy -> suite red.
@@ -64,8 +64,8 @@ run_case() {
   oks=$(printf '%s\n' "$out" | grep -c '^\[OK\]' || true)
   if [[ "$expect" == ok && "$oks" -gt 0 && "$warns" -eq 0 && "$notes" -eq 0 ]]; then
     echo "ok - $label"
-  elif [[ "$expect" == warn && "$warns" -eq 1 ]]; then
-    echo "ok - $label (warned)"
+  elif [[ "$expect" == warn && "$warns" -ge 1 && "$notes" -eq 0 ]]; then
+    echo "ok - $label (warned x$warns)"
   elif [[ "$expect" == note && "$notes" -gt 0 && "$warns" -eq 0 ]]; then
     echo "ok - $label (noted)"
   else
@@ -100,22 +100,29 @@ run_case "empty-string brain home warns (empty != set)" warn \
 # ── state 3: neither present (genuinely unset) → notes, never warn ─────────
 run_case "both unset yields non-authoritative notes" note \
   -u:MOSAIC_HOST_ROOT -u:MOSAIC_BRAIN_HOME
-run_case "both empty-string yields non-authoritative notes" note \
+run_case "both empty-string warns (empty is present, not absent)" warn \
   MOSAIC_HOST_ROOT= MOSAIC_BRAIN_HOME=
+run_case "host empty + brain unset warns" warn \
+  MOSAIC_HOST_ROOT= -u:MOSAIC_BRAIN_HOME
+run_case "host unset + brain empty warns" warn \
+  -u:MOSAIC_HOST_ROOT MOSAIC_BRAIN_HOME=
 
-# ── red control (mutation): empty-vs-unset distinction removed → red ───────
-# Mutant replaces the -n tests with plain set-tests, so an EMPTY value counts
-# as present: the empty-host arm above would flip to pass and the suite reds.
+# ── red control (mutation): presence tracking removed → red ────────────────
+# Mutant regresses to the reviewed defect shape: presence derived from
+# NONEMPTINESS (the `${VAR:-}` collapse) instead of true -v tracking. Both-empty
+# then looks genuinely-absent and is mis-filed as informational; the both-empty
+# warn arm above finds no WARN and the suite reds.
 MUT="$ROOT/mosaic-doctor.mutant"
-sed 's/\[\[ -n "$host_root" \&\& -n "$brain_home" \]\]/[[ -v MOSAIC_HOST_ROOT \&\& -v MOSAIC_BRAIN_HOME ]]/' \
+sed 's/\[\[ -v MOSAIC_HOST_ROOT \]\]  \&\& host_set=1/[[ -n "${MOSAIC_HOST_ROOT:-}" ]] \&\& host_set=1/; s/\[\[ -v MOSAIC_BRAIN_HOME \]\] \&\& brain_set=1/[[ -n "${MOSAIC_BRAIN_HOME:-}" ]] \&\& brain_set=1/' \
   "$DOCTOR" > "$MUT"
 if cmp -s "$DOCTOR" "$MUT"; then
   echo "SKIP red control (mutation anchor not found — sed pattern drifted)" >&2
 else
-  outm=$(env MOSAIC_HOST_ROOT= MOSAIC_BRAIN_HOME="$BRAIN" bash -c \
-    "warn() { echo \"[WARN] \$*\"; }; note() { echo \"[NOTE] \$*\"; return 0; }; pass() { echo \"[OK] \$*\"; return 0; }; $(sed -n "/^check_structure_anchor_provisioning() {/,/^}/p" "$MUT"); check_structure_anchor_provisioning" 2>&1)
-  if printf '%s\n' "$outm" | grep -q '^\[OK\]'; then
-    echo "ok - red control bites (mutant treats empty as present; shipped does not)"
+  mut_fn=$(sed -n "/^check_structure_anchor_provisioning() {/,/^}/p" "$MUT")
+  outm=$(env MOSAIC_HOST_ROOT= MOSAIC_BRAIN_HOME= bash -c \
+    "warn() { echo \"[WARN] \$*\"; }; note() { echo \"[NOTE] \$*\"; return 0; }; pass() { echo \"[OK] \$*\"; return 0; }; $mut_fn; check_structure_anchor_provisioning" 2>&1)
+  if printf '%s\n' "$outm" | grep -q '^\[NOTE\]'; then
+    echo "ok - red control bites (mutant collapses empty into informational; shipped does not)"
   else
     fail "red control did not reproduce the regression shape (mutant output unexpected)"
   fi