feat: integrate seven exact-argv test adapters

[daichunghy]

Summary

This integration PR supersedes #27 and #28.

It combines the two adapter waves into one mergeable branch with seven bundled adapters:

• Bun: bun test
• Deno: deno test
• Elixir Mix: mix test
• Go: existing go test
• Java Maven: mvn test
• Node npm: existing npm test
• Python: existing pytest

The branch resolves the overlapping adapter/test/documentation changes and adds a Bun lockfile
priority regression: a Bun-marked repository must not fall back to a blocking npm test command.
All target execution remains exact-argv, shell: false, opt-in and bounded.

Verification

• npm run verify
• 49 tests across 9 files
• typecheck/build pass
• git diff --check passes

Boundary

Bun, Deno, Elixir and Maven runtimes are not installed in this environment. Their execution
boundaries are tested through the injected executor; no external adapter adoption or npm publication
is claimed.