Match basic-cli Path value behavior

[lukewilliamboswell]

Summary

• support interpolated path literals as UTF-8 paths
• add representation-preserving Str.inspect output
• derive hashing consistently with structural equality
• document and test the added value behavior

This brings the shared package up to the pure-value behavior currently carried by basic-cli. Platform filesystem effects are deliberately deferred to #6, which is waiting on roc-lang/roc#10311.

Dependency

This is stacked on #5 and should be rebased or retargeted to main after #5 merges.

Validation

• ci/all_tests.sh
  • formatting and package check
  • 79 package tests
  • docs and bundle generation
  • bundled example check, test, run, build, and execution