pre-push: refuse a push from a clone outside the felhom workspace (R-204 rider)

The workspace root is already documented (workspace-CLAUDE.md, the workspace-root
CLAUDE.md 'stay inside it') and work drifted into a home directory anyway. A rule
that has failed once as a reminder is not fixed by writing it down again, so it is
now asserted where it can bite.

A push is the right trigger: throwaway clones under /tmp for probes and red-proofs
never push, so nothing legitimate breaks. Symlinks are resolved on both sides; an
absent workspace root SKIPS the check rather than failing it, so this cannot brick
a legitimate clone on another machine. The only bypass is the documented
--no-verify, whose use is already reportable.

Identical in all four repos.

.githooks/pre-push

@@ -29,6 +29,41 @@ root=$(git rev-parse --show-toplevel 2>/dev/null) || {
 }
 cd "$root" || exit 1
 
+# ── WORKSPACE-ROOT ASSERTION (2026-08-05, R-204 rider) ───────────────────────────────────────────
+# Refuse a push from a clone outside the felhom workspace.
+#
+# WHY THIS IS A HOOK AND NOT A LINE IN A DOCUMENT: the workspace root is ALREADY written down, in
+# documentation/runbooks/workspace-CLAUDE.md and in the workspace-root CLAUDE.md ("stay inside it"),
+# and work drifted into a home directory anyway. A rule that has failed once as a reminder is not
+# fixed by writing it down again — it has to be asserted where it can bite.
+#
+# A PUSH IS THE RIGHT TRIGGER, deliberately: throwaway clones under /tmp for probes and red-proofs
+# never push, so nothing legitimate breaks. Reads and builds elsewhere stay unaffected.
+#
+# Symlinks are resolved on BOTH sides before comparison, so a symlinked path neither falsely passes
+# nor falsely fails. If the workspace root does not exist on this machine the check is SKIPPED, not
+# failed — this hook must not brick a legitimate clone on a different host.
+#
+# The only bypass is the documented `git push --no-verify`, whose use is already reportable.
+FELHOM_WORKSPACE_ROOT=/mnt/5_hdd/felhom.eu
+if [ -d "$FELHOM_WORKSPACE_ROOT" ]; then
+    ws_real=$(cd "$FELHOM_WORKSPACE_ROOT" 2>/dev/null && pwd -P) || ws_real=""
+    root_real=$(pwd -P) || root_real=""
+    if [ -n "$ws_real" ] && [ -n "$root_real" ]; then
+        case "$root_real/" in
+            "$ws_real"/*) : ;;  # inside the workspace — proceed
+            *)
+                echo "pre-push: PUSH REFUSED - this clone is OUTSIDE the felhom workspace." >&2
+                echo "          clone:    $root_real" >&2
+                echo "          expected: under $ws_real (repos live in $ws_real/git/<repo>)" >&2
+                echo "          Work in the workspace clone, or bypass with 'git push --no-verify'" >&2
+                echo "          and state that you did in the session report." >&2
+                exit 1
+                ;;
+        esac
+    fi
+fi
+
 if ! command -v python3 >/dev/null 2>&1; then
     echo "pre-push: FAIL - python3 not found, so the gates CANNOT run. This is a failure, never a" >&2
     echo "          pass by default. Install python3, or push with --no-verify and say so." >&2