Rename validate hooks to install hooks

- Rename 13 on_Crawl__00_validate_* hooks to on_Crawl__00_install_*
- This better reflects what these hooks actually do (check/install binaries)
- Update TODO_hook_architecture.md to reflect renamed hooks

archivebox/plugins/git/on_Crawl__00_install_git.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+"""
+Validation hook for git binary.
+
+Runs at crawl start to verify git is available.
+Outputs JSONL for InstalledBinary and Machine config updates.
+"""
+
+import sys
+import json
+
+
+def find_git() -> dict | None:
+    """Find git binary."""
+    try:
+        from abx_pkg import Binary, EnvProvider
+
+        binary = Binary(name='git', binproviders=[EnvProvider()])
+        loaded = binary.load()
+        if loaded and loaded.abspath:
+            return {
+                'name': 'git',
+                'abspath': str(loaded.abspath),
+                'version': str(loaded.version) if loaded.version else None,
+                'sha256': loaded.sha256 if hasattr(loaded, 'sha256') else None,
+                'binprovider': loaded.binprovider.name if loaded.binprovider else 'env',
+            }
+    except Exception:
+        pass
+
+    return None
+
+
+def main():
+    result = find_git()
+
+    if result and result.get('abspath'):
+        print(json.dumps({
+            'type': 'InstalledBinary',
+            'name': result['name'],
+            'abspath': result['abspath'],
+            'version': result['version'],
+            'sha256': result['sha256'],
+            'binprovider': result['binprovider'],
+        }))
+
+        print(json.dumps({
+            'type': 'Machine',
+            '_method': 'update',
+            'key': 'config/GIT_BINARY',
+            'value': result['abspath'],
+        }))
+
+        if result['version']:
+            print(json.dumps({
+                'type': 'Machine',
+                '_method': 'update',
+                'key': 'config/GIT_VERSION',
+                'value': result['version'],
+            }))
+
+        sys.exit(0)
+    else:
+        print(json.dumps({
+            'type': 'Dependency',
+            'bin_name': 'git',
+            'bin_providers': 'apt,brew,env',
+        }))
+        print(f"git binary not found", file=sys.stderr)
+        sys.exit(1)
+
+
+if __name__ == '__main__':
+    main()