This commit contains the following changes:
R {AGENTS.md => for-llm/repo.md}

- Updated example comment to use correct Zig 0.15 addTest syntax
- Replaced deprecated .target, .optimize, .root_source_file with .root_module
- Added version note to clarify this is for Zig 0.15+ syntax
- Removed outdated parameters that no longer exist in current API

- Fixed incorrect test count attribution where all 83 tests were attributed to the last file
- Added proper per-file tracking with separate counters for each test file
- Now correctly reports individual file results (e.g., 'string_literals: 5 of 5 tests passed')
- Maintains global summary showing total test count across all files
- Provides better visibility into test distribution and per-module test health
- Each file's test count is now accurately reported as tests are processed

- Updated test_runner.zig to work with Zig 0.15 API changes
- Replaced complex File.Writer approach with std.debug.print for simplicity
- Fixed stderr access and formatting methods for new Zig version
- Re-enabled custom test runner in build.zig for both lib_unit_tests and exe_unit_tests
- Restored colored test output with individual test visibility
- All 83 tests now pass with improved test runner output formatting