feat: add /convert-to-apple-container skill, remove /convert-to-docker (#324)

Docker is now the default runtime. The /convert-to-apple-container skill
uses the new skills engine format (manifest.yaml, modify/, intent files,
tests/) to switch to Apple Container on macOS.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/convert-to-apple-container/modify/container/build.sh

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+#!/bin/bash
+# Build the NanoClaw agent container image
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+IMAGE_NAME="nanoclaw-agent"
+TAG="${1:-latest}"
+CONTAINER_RUNTIME="${CONTAINER_RUNTIME:-container}"
+
+echo "Building NanoClaw agent container image..."
+echo "Image: ${IMAGE_NAME}:${TAG}"
+
+${CONTAINER_RUNTIME} build -t "${IMAGE_NAME}:${TAG}" .
+
+echo ""
+echo "Build complete!"
+echo "Image: ${IMAGE_NAME}:${TAG}"
+echo ""
+echo "Test with:"
+echo "  echo '{\"prompt\":\"What is 2+2?\",\"groupFolder\":\"test\",\"chatJid\":\"test@g.us\",\"isMain\":false}' | ${CONTAINER_RUNTIME} run -i ${IMAGE_NAME}:${TAG}"

.claude/skills/convert-to-apple-container/modify/container/build.sh.intent.md

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+# Intent: container/build.sh modifications
+
+## What changed
+Changed the default container runtime from `docker` to `container` (Apple Container CLI).
+
+## Key sections
+- `CONTAINER_RUNTIME` default: `docker` → `container`
+- All build/run commands use `${CONTAINER_RUNTIME}` variable (unchanged)
+
+## Invariants
+- The `CONTAINER_RUNTIME` environment variable override still works
+- IMAGE_NAME and TAG logic unchanged
+- Build and test echo commands unchanged
+
+## Must-keep
+- The `CONTAINER_RUNTIME` env var override pattern
+- The test command echo at the end