Close out and publish the final 3.0.0 release

[Andesha]

Summary

This is the closing issue for the Towards 3.0.0 milestone. It must remain open until every other issue in the milestone is closed or formally removed from the milestone with a documented rationale. Once that prerequisite is met, perform the final quality pass and publish EEG2BIDS 3.0.0. This issue owns release-wide code review, documentation polish, final verification, publication, and closure of the milestone rather than new feature development.

Release gate

• This issue is blocked by every other issue assigned to the Towards 3.0.0 milestone.
• New work added to the milestone also becomes a prerequisite for this issue.
• Do not close this issue until 3.0.0 is published and the milestone can be closed.

Scope

Code review

• Review the complete 3.0.0 change set against the previous stable release.
• Check correctness, maintainability, security boundaries, dependency and packaging changes, and removal of obsolete paths.
• Confirm automated tests cover critical conversion, backend, Electron, and packaging behavior.
• Resolve release-blocking findings or track explicitly accepted follow-ups.

Documentation polish

• Review user, installation, development, testing, and troubleshooting documentation for accuracy and consistency with 3.0.0.
• Remove or clearly mark obsolete 2.x instructions and unsupported workflows.
• Verify commands, links, supported-platform statements, and clean-install guidance.
• Prepare concise release notes covering major changes, migrations, known limitations, and breaking changes.

Final release

• Confirm all required work in the Towards 3.0.0 milestone is complete or explicitly deferred.
• Verify versions and release metadata are consistently set to 3.0.0.
• Run the full automated test, build, packaging, and available clean-install/smoke-test workflows.
• Publish the 3.0.0 tag and GitHub release with the approved artifacts, checksums, and release notes.
• Verify the published artifacts and documentation from a clean user perspective.
• Close the Towards 3.0.0 milestone after all release checks succeed.

Acceptance criteria

• The full 3.0.0 change set has received a documented final code review.
• All release-blocking review findings are resolved.
• User-facing and contributor documentation accurately describes 3.0.0.
• Obsolete 2.x guidance is removed or clearly identified.
• Release notes document major changes, breaking changes, migration steps, and known limitations.
• Every other issue in the milestone is closed, or removed from the milestone with a documented rationale.
• No open 3.0.0 release blockers remain.
• Version numbers and release metadata consistently identify 3.0.0.
• Required tests, production builds, and smoke tests pass.
• The 3.0.0 tag and GitHub release are published with all required artifacts and checksums.
• Published artifacts and key documentation links are verified after release.
• The Towards 3.0.0 milestone is closed as part of completing this issue.

Non-goals

• Adding new features that are not required to make 3.0.0 releasable.
• Expanding the supported platform or package matrix during the final release pass.
• Silently deferring release-blocking defects without a documented decision.

[Andesha]

Release testing note: test both installation and uninstallation on clean machines/VMs with no development tools or preinstalled developer dependencies. This should verify that end-user install and uninstall flows work without relying on compilers, package managers, runtimes, SDKs, or other tooling present only on developer systems.

[Andesha]

Final packaging QA note: add one frontend regression check for #91 confirming that a nested parameter JSON prepopulates Project, Subproject, Visit, Site, LineFrequency, Reference, and RecordingType once, and that later user edits are not overwritten by metadata rereads.