fix: portable mod.nu path in tests, recommend mod.nu in README

[Copilot]

Two issues from PR review: hardcoded absolute path in the mod.nu integration test broke on any non-workspace clone, and the README still pointed users at the completions file directly instead of the new stable mod.nu entrypoint.

Changes

• tests/completions.test.nu — compute mod.nu path dynamically from $env.FILE_PWD instead of embedding a hardcoded workspace path:

  let mod-path = ([$env.FILE_PWD ".." "mod.nu"] | path join | path expand)
  let out = ^nu --no-config-file -c $"
      use '($mod-path)' *
      ...

• README.md — promote mod.nu to the recommended manual install entry point; list the bare completions file as an alternative:

  # Recommended
  use /path/to/dagger.nu/mod.nu *
  
  # Alternative
  use /path/to/dagger.nu/completions/dagger.nu *

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[Copilot]

Pull request overview

This PR fixes portability issues in the Nushell integration test by removing a hardcoded absolute module path, and updates the README to recommend the stable mod.nu entrypoint for manual installs.

Changes:

• Update tests/completions.test.nu to compute the repository mod.nu path dynamically from $env.FILE_PWD.
• Update README.md to recommend mod.nu as the primary manual-install entry point (with completions/dagger.nu as an alternative).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/completions.test.nu	Removes hardcoded absolute path; builds mod.nu path dynamically for portability.
README.md	Documents mod.nu as the recommended entrypoint; keeps direct completions import as an alternative.

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[Copilot]

The new variable name mod-path is inconsistent with the rest of this test file, which uses snake_case (e.g., all_tests). Consider renaming to mod_path (and updating the interpolation) for consistency and to avoid any potential parsing ambiguity around - in variable references.

[danielbodnar]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Renamed mod-path → mod_path in commit 5cba432 to match the snake_case convention used throughout the test file.