libaprs-engine v3.0.0-rc.1

libaprs-engine v3.0.0-rc.1

BLUF

• v3.0.0-rc.1 is the first release candidate for the next major release line.
• No intentional public API break is approved in this release candidate.
• Existing 2.6.0 users should only need dependency-version changes for RC
  testing.
• Raw-byte preservation, fail-closed malformed packet handling, bounded
  transport input, and caller-owned runtime policy remain unchanged.
• The RC must pass local release gates, remote CI, security checks, semver
  review, downstream smoke, and supply-chain evidence checks before final
  v3.0.0.

Changes

• Bumped all workspace crates to 3.0.0-rc.1.
• Updated current README, API, transport, publishing, APRS-IS profile, and
  downstream-smoke examples to target 3.0.0-rc.1.
• Added v3.0.0 migration guidance that documents the no-intentional-break
  migration from 2.6.0.
• Updated the v3.0.0 breaking-change decision record so future breaking
  changes remain evidence-gated.
• Added a docs gate requiring RC release notes, migration guidance, and release
  preparation evidence to stay in sync.

Security Notes

• Packet and transport input remains untrusted.
• Accepted packets must preserve raw bytes exactly.
• Malformed packet shape must fail closed.
• Applications should pin the exact RC version during testing and report any
  source, semver, or behavior regression before final 3.0.0.
• Post-publication downstream smoke must regenerate its lockfile from crates.io
  so checksum evidence matches the published RC crates.

Release Gates

• scripts/verify-docs.sh
• scripts/test-supply-chain-evidence.sh
• scripts/verify-release.sh
• cargo semver-checks check-release -p libaprs-engine when available
• Post-publication downstream smoke against 3.0.0-rc.1

Upgrade Notes

Existing 2.6.0 users can test the release candidate by updating dependency
versions to =3.0.0-rc.1. No source changes are expected.