RSpec reporter does not follow ADR-009 and ADR-010 for project root configuration

[Hiro-Chiba]

Summary

The RSpec reporter has not adopted ADR-009 (relax path validation) or ADR-010 (drop silent cwd fallback). PHPUnit (#151), Go (#153), Rust (#154) are already updated.

Current Behavior

reporters/rspec/lib/tdd_guard_rspec/formatter.rb:179-186:

return DEFAULT_DATA_DIR unless project_root && !project_root.empty?  # ADR-010
return DEFAULT_DATA_DIR unless absolute_path?(project_root)          # ADR-009

Relative paths are rejected and an unset env var silently falls back to cwd.

Expected Behavior

Resolve relative paths via File.expand_path and raise an error when no project root is configured. Mirror PR #151.