fix(init): refuse to copy the install tree onto itself

copyFilesFromLocal ran `rm -rf "$script_dir"` before ever reading the source. When
source and destination resolve to the same path — which is what happens if you
run `sudo ./init.sh init` from inside /libreportal-system/install, an easy
mistake when re-running to re-bake the footprint — the rm deletes the source too,
the copy then fails, and the script exits.

The damage is worse than a failed copy: it exits before initRootHelpers and
before the sudoers tightening, so the install tree is gone AND the manager is
left holding the install-phase grant (ALL=(ALL) NOPASSWD: ALL) instead of the
scoped allowlist. I did exactly this on a live box; the tree was recoverable from
git, but the loose sudo rule is the part that matters.

Now: resolve both paths and refuse if they match, and validate the source before
destroying the destination rather than after. Both checks run ahead of the rm.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

init.sh

@@ -453,7 +453,32 @@ copyFilesFromLocal() {
     fi
     
     isHeader "Copying from Local Directory"
-    
+
+    # Refuse to copy a directory onto itself. Everything below deletes the
+    # destination BEFORE reading the source, so when the two resolve to the same
+    # path the rm wipes the source too and the copy fails with the tree already
+    # gone — taking the install down and stopping short of the root-helper bake
+    # and the sudoers tightening, leaving install-phase sudo in place.
+    # Running `sudo ./init.sh init` from inside the install tree is enough to hit
+    # it, which is an easy mistake when re-running to re-bake the footprint.
+    local _src_real _dst_real
+    _src_real="$(readlink -f "$source_dir" 2>/dev/null || echo "$source_dir")"
+    _dst_real="$(readlink -f "$script_dir" 2>/dev/null || echo "$script_dir")"
+    if [[ "$_src_real" == "$_dst_real" ]]; then
+        isError "Source and destination are the same directory ($_dst_real)."
+        isNotice "Run init.sh from your source checkout, not from inside the install tree."
+        exit 1
+    fi
+
+    # Validate the source BEFORE destroying the destination, for the same reason:
+    # a bad source used to be discovered only after the install tree was gone.
+    # detectLocalLibrePortal derives the directory the same way source_dir is
+    # derived above, so it checks exactly what is about to be copied.
+    if ! detectLocalLibrePortal >/dev/null 2>&1; then
+        isError "$source_dir is not a valid LibrePortal source — refusing to replace $script_dir."
+        exit 1
+    fi
+
     # Remove existing install directory
     sudo rm -rf "$script_dir"