Add .harperignore for Watched Files & Deploys

### Feature Summary

Add support for a new file, `.harperignore`, which will be used to ignore files when watching for changes, and will ignore files when building up for `harper deploy`.

### Problem This Solves

Without this, to do a limited deployment, I have to create a sub-directory and copy artifacts into it, then `harper deploy target=AppName` within it. The watched files doesn't have a workaround.

### Proposed Solution

Create the ignore file.

### Priority/Impact

None

### Examples or References

_No response_

Start by locating the watched-files flow and the `harper deploy` entry point, then determine how `.harperignore` should be discovered and interpreted in both paths. Done means the same ignore file supports limited deployment and excludes matching files from change watching.

Written by the indexing model from the issue text.