Add test session result drilldown

[thebiglabasky]

Summary

Adds checkly test-sessions get --result/-r so users can drill into a single recorded test session result with the same detail formatting used by checkly checks get --result.

Changes

• Adds a REST client method for GET /v1/test-sessions/:id/results/:resultId.
• Reuses the existing check-result detail formatter for test-session result output.
• Adds a shared renderCommandHints() formatter for aligned command hints and uses it across result drilldowns plus existing list/detail navigation hint formatters.
• Covers detail, JSON, watch behavior, and REST path mapping with focused tests.

Backend dependency

The /test-sessions/<id>/results/<result-id> endpoint has been deployed, so this CLI PR is not blocked on an unmerged backend change.

Validation

• pnpm exec vitest --run ./src/formatters/__tests__/check-result-detail.spec.ts ./src/formatters/__tests__/render.spec.ts ./src/formatters/__tests__/test-sessions.spec.ts ./src/commands/__tests__/test-sessions-get.spec.ts ./src/rest/__tests__/test-sessions.spec.ts
• pnpm exec eslint src/formatters/render.ts src/formatters/check-result-detail.ts src/formatters/checks.ts src/formatters/test-sessions.ts src/formatters/alert-channels.ts src/formatters/account-members.ts src/formatters/status-pages.ts src/formatters/batch-stats.ts src/commands/checks/get.ts
• pnpm --filter checkly exec tsc --noEmit --pretty false
• CHECKLY_SKIP_AUTH=1 ./bin/run test-sessions get --help
• git diff --check