#14469: feat: Add automatic pnpm install to shell hook

- Added 'pnpm install' command to the shellHook in flake.nix - This ensures all project dependencies are automatically installed when entering the development environment - Improves developer experience and ensures consistent setup <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds a new `flake.nix` that defines an OpenClaw `devShell` with Node/TypeScript/pnpm, and a `shellHook` that sets the npm registry and runs `pnpm install` when entering `nix develop`. The main concern is that the change is much broader than the PR description: it introduces a full flake with additional (currently unused) inputs/modules (process-compose/services-flake/northwind) and a demo-style description. Additionally, the `shellHook` has persistent side effects (`npm set registry ...` writes to user config) and runs installs unconditionally on every shell entry, which can break offline/restricted environments and unexpectedly mutate the repo. <h3>Confidence Score: 2/5</h3> - This PR is not safe to merge as-is due to broad, likely unintended dev-environment changes and persistent side effects in the shell hook. - The change introduces a full new flake with unrelated/demo inputs beyond the stated goal, and the dev shell hook persistently modifies user npm config and runs `pnpm install` on every entry (network + working-tree mutations). These are high-friction behaviors that would affect all Nix dev-shell users. - flake.nix <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->