Clarify PTxray benefits, open source, and assessment safety

[John-PTS]

The public README moves from a brief introduction directly into release downloads and commands, leaving the benefits and open-source license difficult to discover. This revision leads with the questions PTxray helps answer, the evidence and reports users receive, and the Apache-2.0 assessment code. Release history has a secondary section at the end.

Safety is explained through specific behavior: no system configuration changes or remediation, no network calls during assessment, no assessment-data uploads, separate disclosed acquisition, and verifiable signed releases. Privileged execution, local writes, manual evidence gaps, vendor inputs, and report-sharing limits remain explicit.

Validation: all 22 public-page tests pass; release version/count checks, README section/local links, and whitespace checks pass.

Suggested GitHub About description for review:

Free, open-source health and security assessment for IBM AIX and IBM i. Local reports reveal risks, patch gaps, and operational issues. No configuration changes or assessment-data uploads.