Fix two docs/UX errors found during Mac install (tor-ms22)

1. 'mempalace init --yes' without a dir argument fails — 'dir' is
   required. The semantics were wrong too: 'mempalace init' is
   per-project (sets up mempalace.yaml + entity detection in a specific
   directory), not a one-time global init. The palace itself is
   created lazily on first write, so neither mempalace-session nor
   mempalace-docs requires any init step.

   Removed the misleading 'One-time palace init' block from README.md,
   ARCHITECTURE.md, and SKILL.md. Added a clarifying note:
   'mempalace init <dir>' is per-project and optional (needed only to
   customize the wing name or entity detection before mempalace-docs).

2. install.sh's 'Skipping <name>: <dest> exists and is not our symlink'
   warning gave no actionable guidance. On the Mac, a leftover
   ~/.local/bin/mempalace-docs (likely from the pre-split cli_utils
   days) was blocking the new install and the user had no easy way
   to know what to do about it.

   Expanded the warning to:
   - Show whether the blocker is a symlink (and what it points at) or
     a real file.
   - Print the exact 'rm && ./install.sh' fix line.
   - Track skipped count separately and flag it in the closing
     summary so a scrolling user doesn't miss it.

   Added matching troubleshooting paragraph to the README 'Install
   mempalace-toolkit' section explaining the skip behaviour and
   pointing at the installer's own message for the fix.

Smoke-tested the new skip-warning code path by temporarily replacing
~/.local/bin/mempalace-docs with a foreign symlink and re-running
install.sh — output is clear, specific, and restores cleanly.

install.sh

@@ -76,6 +76,7 @@ install_bin() {
     mkdir -p "$BIN_DEST"
     note "Symlinking bin/ executables into $BIN_DEST"
     local count=0
+    local skipped=0
     for src in "$BIN_SRC"/*; do
         [[ -x "$src" && -f "$src" ]] || continue
         local name; name=$(basename "$src")
@@ -86,7 +87,17 @@ install_bin() {
                 count=$((count+1))
                 continue
             else
-                warn "Skipping $name: $dest exists and is not our symlink"
+                # Tell the user exactly what's in the way and how to fix it.
+                local what="real file"
+                if [[ -L "$dest" ]]; then
+                    local current_target
+                    current_target=$(readlink "$dest")
+                    what="symlink → $current_target"
+                fi
+                warn "Skipping $name — $dest already exists ($what)"
+                printf '       If stale (e.g. an old cli_utils install), remove and re-run:\n'
+                printf '           rm %q && %q/install.sh\n' "$dest" "$SCRIPT_DIR"
+                skipped=$((skipped+1))
                 continue
             fi
         fi
@@ -96,6 +107,9 @@ install_bin() {
     done
     echo
     ok "Installed $count executable(s)"
+    if (( skipped > 0 )); then
+        warn "$skipped executable(s) skipped — see notes above"
+    fi
 }
 
 install_skill() {