refactor(claude): migrate hooks to external scripts and add new hooks

Replace inline command strings in settings.json with external scripts
in .claude/hooks/ for readability and maintainability. Consolidate
three PostToolUse formatters into one script and add markdown/yaml
formatting. Add new hooks: SessionStart context banner, Stop lint
gate, async Bats test runner, idle desktop notification, and
PostToolUseFailure logger.

.claude/hooks/pre-edit-block.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+# Pre-edit guard: block vendor/lock files and secrets.d real fish files.
+# Receives tool input JSON on stdin.
+
+fp=$(jq -r '.tool_input.file_path // empty')
+[ -z "$fp" ] && exit 0
+
+case "$fp" in
+  */fzf-tmux | */yarn.lock | */.yarn/*)
+    echo "BLOCKED: $fp is a vendor/lock file — do not edit directly" >&2
+    exit 2
+    ;;
+  */secrets.d/*.fish)
+    case "$(basename "$fp")" in
+      *.example.fish | *.fish.example) exit 0 ;;
+    esac
+    echo "BLOCKED: do not edit $fp directly — it is gitignored." >&2
+    echo "Copy the matching .fish.example file and edit that locally." >&2
+    exit 2
+    ;;
+esac
+
+exit 0