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/post-edit-format.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# Post-edit formatter: auto-format file based on extension.
+# Receives tool output JSON on stdin.
+
+fp=$(jq -r '.tool_input.file_path // empty')
+[ -z "$fp" ] || [ ! -f "$fp" ] && exit 0
+
+case "$fp" in
+  *.sh | */bin/*)
+    head -1 "$fp" | grep -qE '^#!.*(ba)?sh' \
+      && command -v shfmt > /dev/null \
+      && shfmt -i 2 -bn -ci -sr -fn -w "$fp"
+    ;;
+  *.fish)
+    command -v fish_indent > /dev/null && fish_indent -w "$fp"
+    ;;
+  *.lua)
+    command -v stylua > /dev/null && stylua "$fp"
+    ;;
+  *.md)
+    command -v biome > /dev/null && biome format --write "$fp" 2> /dev/null
+    command -v markdown-table-formatter > /dev/null \
+      && markdown-table-formatter "$fp" 2> /dev/null
+    ;;
+  *.yml | *.yaml)
+    command -v prettier > /dev/null && prettier --write "$fp" 2> /dev/null
+    ;;
+esac
+
+exit 0