Fix Synology runner home and add MIT license

[jmcte]

Summary

• move the live runner home into the writable state mount instead of writing mutable files under /actions-runner
• update the smoke harness to exercise the read-only runner source and writable runner home split
• add the MIT license and bump the published image/sample config to 0.1.2

Verification

• bash -n docker/runner-entrypoint.sh
• bash -n scripts/smoke-test.sh
• pnpm lint
• pnpm test
• pnpm build
• pnpm validate-config -- --config config/pools.yaml --env .env.example
• DOCKER_CONTEXT=colima pnpm smoke-test
• DOCKER_CONTEXT=colima ./scripts/build-image.sh ghcr.io/omt-global/synology-github-runner:0.1.2 --push
• docker --context colima manifest inspect ghcr.io/omt-global/synology-github-runner:0.1.2

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: c59ba2e31f

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".