refactor(hooks): rename to gt tap guard pr-workflow

Reorganizes Claude Code hook handlers under `gt tap` namespace:
- gt tap - parent command for all hook handlers
- gt tap guard - subcommand for blocking operations
- gt tap guard pr-workflow - blocks PR creation and feature branches

This structure allows future expansion:
- gt tap audit <x>   - logging/metrics (PostToolUse)
- gt tap inject <x>  - input modification (PreToolUse)
- gt tap check <x>   - validation (PostToolUse)

Replaces the flat gt block-pr-workflow command.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/tap.go

@@ -0,0 +1,35 @@
+package cmd
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var tapCmd = &cobra.Command{
+	Use:   "tap",
+	Short: "Claude Code hook handlers",
+	Long: `Hook handlers for Claude Code PreToolUse and PostToolUse events.
+
+These commands are called by Claude Code hooks to implement policies,
+auditing, and input transformation. They tap into the tool execution
+flow to guard, audit, inject, or check.
+
+Subcommands:
+  guard   - Block forbidden operations (PreToolUse, exit 2)
+  audit   - Log/record tool executions (PostToolUse) [planned]
+  inject  - Modify tool inputs (PreToolUse, updatedInput) [planned]
+  check   - Validate after execution (PostToolUse) [planned]
+
+Hook configuration in .claude/settings.json:
+  {
+    "PreToolUse": [{
+      "matcher": "Bash(gh pr create*)",
+      "hooks": [{"command": "gt tap guard pr-workflow"}]
+    }]
+  }
+
+See ~/gt/docs/HOOKS.md for full documentation.`,
+}
+
+func init() {
+	rootCmd.AddCommand(tapCmd)
+}