docs: prepare v1.2.0 publication metadata

[gcomneno]

Summary

Prepares the repository for the v1.2.0 publication checkpoint without changing runtime behavior.

Documentation

• aligns authoritative English documentation with the current command surface and 465-test release-candidate suite;
• updates the derived Italian public documentation for the same user-facing areas;
• documents db ask with a tracked historical database for reproducible examples;
• clarifies that real-model availability is separate from semantic qualification;
• records that the currently evaluated reference local models remain NOT QUALIFIED for semantic read queries;
• corrects the repeated-digit semantics in reproducibility documentation.

Publication metadata

• adds CITATION.cff for GitHub/Zenodo citation metadata;
• adds CHANGELOG.md with the v1.2.0 publication scope and v1.1.0 baseline;
• links publication metadata from the documentation index.

Validation

• 465 Python tests run, 2 skipped;
• documentation stale-pattern audit passed;
• tracked SQLite example database verified;
• citation metadata validation passed;
• relative Markdown link validation passed;
• CLI discovery and db ask help validation passed;
• git diff --check passed;
• staged manifest contains only the 9 documentation/metadata files.

No application or research-engine code is modified.

Commit: c2dadf97e7aa3dfd6c312f034978756974303b4b