feat: package as a Claude Code plugin with a deterministic quality gate

Workflows move to skills/<name>/SKILL.md so the repo installs as a plugin.
scripts/quality-gate runs only the checks of the requested tier on the diff
and reports missing tools as unverified instead of passing them. Hooks block
stopping on a failed or stale gate, guard destructive shell commands and
format edited files with the project's own formatter.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

hooks/hooks.json

@@ -0,0 +1,27 @@
+{
+  "hooks": {
+    "PreToolUse": [
+      {
+        "matcher": "Bash",
+        "hooks": [
+          { "type": "command", "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/scripts/hooks/bash_guard.py\"" }
+        ]
+      }
+    ],
+    "PostToolUse": [
+      {
+        "matcher": "Edit|Write|MultiEdit",
+        "hooks": [
+          { "type": "command", "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/scripts/hooks/post_edit.py\"", "timeout": 60 }
+        ]
+      }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          { "type": "command", "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/scripts/hooks/stop_gate.py\"" }
+        ]
+      }
+    ]
+  }
+}