Synchronize v1.6.19 public launch metadata

[masarray]

Public-launch P0 fixes

• mark ARSAS 1.6.19 as the published 2026-08-01 release in CHANGELOG.md
• add an Unreleased section for post-release IED-card fixes already merged through Fix IED relay fascia status placement and QA #128
• update CITATION.cff from 1.6.16 to 1.6.19
• expose the exact stable version as v{{STABLE_VERSION}} in website navigation
• trigger the product website validation and GitHub Pages deployment path after merge

Validation completed

• product website source and rendered-build validation passed
• verified stable release evidence for v1.6.19 passed
• SEO, privacy, consent, internal-link, search-authority, adoption-proof and responsive-media checks passed
• application source/license and release invariants passed
• solution restore and Release build passed
• ARSAS application regression tests passed
• portable x64 publish and artifact upload passed

Merge

Squash-merged to main as ead720afc22e34988977daee3da9b44c05c1c590. The landing change is within the production Pages workflow path, so the merge triggers the normal build, deployment and public-attestation pipeline.

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.
To continue using code reviews, you can upgrade your account or add credits to your account and enable them for code reviews in your settings.