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.

ARCHITECTURE.md

@@ -147,14 +147,14 @@ cd ~/mempalace-toolkit
 # 3. Ensure ~/.local/bin is on PATH (installer warns if not)
 export PATH="$HOME/.local/bin:$PATH"
 
-# 4. Initialize palace if needed (one-time, platform-wide)
-mempalace init --yes
-
-# 5. Mine opencode history into the palace
+# 4. Mine opencode history into the palace
+#    (No global init step needed — the palace is created on first write.
+#     `mempalace init <dir>` is per-project, not global, and is optional.)
 mempalace-session --dry-run              # preview scope
 mempalace-session                        # do it for real (~20 min for ~60 sessions)
 
-# 6. Mine project docs (per project)
+# 5. Mine project docs (per project — run `mempalace init --yes <dir>`
+#    first if you want to customize the wing name or entity detection)
 mempalace-docs /workspace/my_project --dry-run
 mempalace-docs /workspace/my_project