Prepare ISRAS 0.1.2 release

[kb2vhn]

Purpose

Finalize the stable ISRAS 0.1.2 release-source candidate after acceptance of the project-initialization and reusable hosted-validation boundary.

Release identity

• Set VERSION and the repository-owned validator identity to stable 0.1.2.
• Finalize the dated 0.1.2 changelog section.
• Add complete 0.1.2 release notes.
• Update README and project-adoption status to describe the stable candidate truthfully.

Included boundary

ISRAS 0.1.2 adds fail-closed initialization of a clean Go project from one exact accepted release and immutable reusable hosted validation using the digest-bound published validator.

Assurance boundary

This pull request does not:

• create or push isras-v0.1.2;
• build or publish release assets;
• create a GitHub Release;
• move main;
• modify Iron File Intelligence or another consuming project;
• claim release completion before signed-tag and six-asset publication verification.

Validation

• Exact six-file release-source boundary.
• Complete Go test suite.
• Race test suite.
• Static analysis and complete build.
• Repository validator build.
• Exact committed-candidate validation with pinned govulncheck@v1.6.0.
• Signed candidate commit verification.