fix(tests): tests no longer reach a real herdr server - a *-shim ancestor hid the mock, the sandbox kept the pane's socket

A suite run from an agent pane with --basetemp .../pytest-pr56-shim left
seven workspaces on that pane's real server (multi-agent-mux):
- the real-herdr resolvers (lib.sh _is_shim_path and the generated shim)
  skipped every PATH directory with "-shim" anywhere in its path, so the
  basetemp hid the mock's bin/ and the real herdr ran; only a directory
  that is itself *-shim is a wrapper now;
- mam_sandbox kept HERDR_SOCKET_PATH (and the pane/tab ids), which the real
  herdr follows over the sandbox HOME; it drops them now.

tests/test_herdr_real_server_leak.py: L1 (ancestor *-shim, both resolvers)
and L2 (pane routing dropped) fail before the fix; L1b keeps a *-shim
wrapper directory excluded.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/lib.sh

@@ -112,9 +112,15 @@ _canonical_file() {
 
 _is_shim_path() {
   case "/$1/" in
-    *"/.mam/shim/"*|*-shim/*|*"$_HERDR_SHIM_DIR_PATTERN"*|*"$_HERDR_SKILLS_BIN_PATTERN"/*)
+    *"/.mam/shim/"*|*"$_HERDR_SHIM_DIR_PATTERN"*|*"$_HERDR_SKILLS_BIN_PATTERN"/*)
       return 0 ;;
   esac
+  # A wrapper directory named *-shim, the directory itself only: an ancestor
+  # such as a pytest basetemp "pytest-x-shim" above a mock's bin/ made the
+  # resolver skip the mock and run the real herdr.
+  case "${1%/}" in
+    *-shim) return 0 ;;
+  esac
   return 1
 }
 
@@ -127,7 +133,7 @@ _resolve_real_herdr_path() {
     [ -x "$dir/herdr" ] || continue
     cand="$(_canonical_file "$dir/herdr" 2>/dev/null)" || cand="$dir/herdr"
     [ -n "$cand" ] || cand="$dir/herdr"
-    _is_shim_path "$cand" && continue
+    _is_shim_path "$(dirname "$cand")" && continue
     real_path="$dir/herdr"
     break
   done
@@ -167,7 +173,7 @@ _resolve_real_herdr() {
   local dir save_ifs="$IFS" real_path=""
   IFS=:
   for dir in $PATH; do
-    if [[ "$dir" != *".mam/shim"* ]] && [[ "$dir" != *"-shim"* ]] && [ -x "$dir/herdr" ]; then
+    if [[ "$dir" != *".mam/shim"* ]] && [[ "${dir%/}" != *-shim ]] && [ -x "$dir/herdr" ]; then
       real_path="$dir/herdr"
       break
     fi