feat(meta): replace sprint workflow with kanban + milestones (D-221)

Sprint-based workflow (38 sprints) replaced by kanban + milestones.
Milestones are many-to-many with tickets and can block each other.

New: /whats-next skill (dependency-driven batch selection with Si
refinement review), /pr-process skill (renamed from pr-push, adds
review comment pickup), clerk agent + pre-push hook for D-record
consistency checks.

Deleted: sprint CLI, sprint-start/sprint-plan/sprint-status skills,
team-scoped file restrictions. Si rewritten as refinement manager.
All 19 agent briefings updated from stale PROJECT_STATE.md reference
to live ticket milestone queries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.config/hooks/pre-push

@@ -190,6 +190,26 @@ else
     echo "pre-push: systems.db not in push — skipping stamp check"
 fi
 
+# --- Clerk review (D-221) ---
+# Spawns the clerk agent to check D-record consistency against the diff.
+# Optional: only runs if tooling/clerk-review exists and is executable.
+# Set SR_SKIP_CLERK=1 to bypass (e.g. for trivial doc-only pushes).
+if [ -x "$REPO_ROOT/tooling/clerk-review" ] && [ "${SR_SKIP_CLERK:-0}" != "1" ]; then
+    echo "pre-push: running clerk review..."
+    CLERK_VERDICT=$("$REPO_ROOT/tooling/clerk-review" 2>&1 | tee /dev/stderr | tail -1)
+    if [ "$CLERK_VERDICT" = "APPROVED" ]; then
+        echo "pre-push: clerk — APPROVED"
+    elif [ "$CLERK_VERDICT" = "TIMEOUT" ]; then
+        echo "pre-push: clerk — TIMEOUT (findings may arrive later at .cache/pre-push-review.md)"
+        ERRORS=$((ERRORS + 1))
+    else
+        echo "pre-push: clerk — REJECTED (see .cache/pre-push-review.md)"
+        ERRORS=$((ERRORS + 1))
+    fi
+else
+    echo "pre-push: clerk review — skipped (not installed or SR_SKIP_CLERK=1)"
+fi
+
 if [ "$ERRORS" -gt 0 ]; then
     echo ""
     echo "pre-push: $ERRORS check(s) failed. Push aborted."