P1.1 · Scaffold Obsidian plugin repo

What

Fork obsidianmd/obsidian-sample-plugin template. Wire up TypeScript strict mode, esbuild, and hot-reload in a local test vault (symlink the built plugin into YourVault/.obsidian/plugins/obsidian-linear-sync).

Acceptance criteria

• npm run dev watches and rebuilds on save.
• Plugin toggles on in Obsidian Settings → Community plugins → Installed.
• A "Linear Sync: Hello" command is registered and shows a Notice.
• CI on GitHub Actions runs type-check on push.

Notes

• Use obsidian@latest peer dep; target Obsidian 1.5+.
• Enable esbuild --external:obsidian so bundle doesn't include Obsidian APIs.