Record v3.0.0-rc.1 release evidence

[Elodie Mirza (elodiejmirza)]

BLUF

• Records completed v3.0.0-rc.1 release evidence after crates.io publication and GitHub prerelease verification.
• Refreshes downstream smoke lockfile to published 3.0.0-rc.1 checksums.
• Syncs ROADMAP.md with GitHub Project chore: harden security robustness gates #3: RC is Done and final v3.0.0 is In progress.

Release evidence

• Tag/release commit: v3.0.0-rc.1 at f5612574181ba13254c82cbe3a6dd9667ee95ccf.
• GitHub Release: https://github.com/SoloSentryOrg/libaprs-engine/releases/tag/v3.0.0-rc.1, prerelease and not latest.
• crates.io: all workspace crates published as 3.0.0-rc.1 and verified unyanked through the crates.io API.
• GitHub latest remains stable v2.6.0.
• GitHub Project chore: harden security robustness gates #3 item v3.0.0-rc.1: Major Release Candidate marked Done with target date 2026-05-04; v3.0.0: Final Major Release moved to In progress.

Verification

• scripts/verify-docs.sh passed.
• scripts/test-supply-chain-evidence.sh passed.
• scripts/check-downstream-smoke-versions.sh passed.
• cargo check --manifest-path examples/downstream-smoke/Cargo.toml --locked --offline passed.
• Dependent crate cargo package validation passed for all transport crates and aprs-cli.
• scripts/check-secrets.sh passed.
• git diff --check passed.

Secure review

• No open findings. This PR records release evidence, lockfile checksums, and roadmap state only; no parser, transport, policy, workflow, or publishing behavior is changed.