fix(freeze): deny paths over PATH_MAX before the quadratic walk (#3623)

A PreToolUse hook that outlives the host's timeout does not block the edit,
and the component walk is quadratic in path length. Deny a file_path over
4096 characters, and links that grow the walk past 8192, before walking.

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

freeze/bin/check-freeze.sh

@@ -168,6 +168,12 @@ _FREEZE_CR=$'\r'
 case "$FILE_PATH" in
   *"$_FREEZE_NL"*|*"$_FREEZE_CR"*) _freeze_unresolved "$TOOL_LABEL $FILE_PATH" "a line break in the path" ;;
 esac
+# The walk below costs time quadratic in the path length, and a hook that
+# outlives the host's timeout lets the edit through. No real path is longer
+# than PATH_MAX (4096 on Linux), so bound the work before it starts.
+if [ "${#FILE_PATH}" -gt 4096 ]; then
+  _freeze_unresolved "$TOOL_LABEL path of ${#FILE_PATH} characters" "longer than 4096 characters"
+fi
 
 # A leading ~ is the home directory to the host's file tools, never a
 # directory named '~' under cwd: joined onto cwd, '~/.zshrc' passed whenever
@@ -227,7 +233,8 @@ esac
 #      POSIX file name. On a POSIX host a Windows path names no local file,
 #      so it is resolved as text and no local symlink is followed.
 # Returns 1 for a symlink loop, a chain over 40 links, an unreadable or
-# line-broken link, or an unplaceable Windows name; the caller fails closed.
+# line-broken link, links that grow the path past 8192 characters, or an
+# unplaceable Windows name; the caller fails closed.
 _resolve_path() {
   local _rem="$1" _win="${3:-0}" _lead="" _cur="" _n=0 _min=0 _reroot=1
   local _part _tgt _p _tail="" _hops=0 _probe=1
@@ -283,6 +290,7 @@ _resolve_path() {
     fi
     case "$_tgt" in /*) _reroot=1 ;; esac
     _rem="${_tgt%/}${_rem:+/$_rem}"
+    [ "${#_rem}" -le 8192 ] || return 1
   done
   _p="$_lead$_cur"
   if [ "${2:-}" != lexical ] && [ "$_probe" = 1 ]; then

test/hook-scripts.test.ts

@@ -1546,6 +1546,17 @@ describe('check-freeze.sh', () => {
       });
     });
 
+    // The walk is quadratic in path length, and a PreToolUse hook that times
+    // out does not block the edit; an over-long path must deny fast.
+    test('a path longer than PATH_MAX denies quickly instead of stalling the hook', () => {
+      withTree(({ base, home, src }) => {
+        const started = Date.now();
+        expect(decide(src, src + '/a/..'.repeat(20000) + '/../outside/x.ts', home, base)).toBe('deny');
+        expect(Date.now() - started).toBeLessThan(4000);
+        expect(decide(src, src + '/a/..'.repeat(500) + '/x.ts', home, base)).toBe('allow');
+      });
+    });
+
     test('Windows separators: a C:\\ dotdot escape through a missing directory denies, a new C:\\ subdirectory allows', () => {
       withTree(({ base, home }) => {
         expect(decide('C:\\dev\\proj\\src', 'C:\\dev\\proj\\src\\..\\..\\other\\new\\x.ts', home, base)).toBe('deny');