chore: remove duplicate hook setup

Keep pre-commit configuration as the single validation path and tolerate deleted tracked Markdown during link validation.

.githooks/pre-commit

@@ -1,5 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-repo_root="$(git rev-parse --show-toplevel)"
-cd "$repo_root"
-exec scripts/validate-repo.sh

agent.md

@@ -1 +0,0 @@
-AGENTS.md

scripts/validate-repo.sh

@@ -108,6 +108,11 @@ files = sorted(set(pathlib.Path(f) for f in tracked + untracked))
 link_re = re.compile(r'\[[^\]]*\]\(([^)]+)\)')
 errors = []
 for f in files:
+    # `git ls-files` includes paths deleted in the working tree. They cannot
+    # contain links and must not make validation fail before their deletion is
+    # staged.
+    if not f.exists():
+        continue
     try:
         text = f.read_text(encoding='utf-8')
     except UnicodeDecodeError: