release: AHP 0.3.0

[connor4312]

Cuts AHP 0.3.0 across all six artifacts (spec + Rust + Kotlin + TypeScript + Swift + Go) and prepares the tree for the next development cycle on 0.4.0.

Commits

1. release: AHP 0.3.0 across all clients — SHA b639a27ee048c77bc262889d813db2295623e425. This is the commit every release tag must point at.

   • Date-stamps every ## [0.3.0] changelog entry to 2026-06-05.
   • Bumps every client manifest from 0.2.0 / 0.1.0 → 0.3.0:
     • clients/rust/Cargo.toml ([workspace.package] + workspace dep pins) + refreshed Cargo.lock.
     • clients/kotlin/gradle.properties (VERSION_NAME).
     • clients/typescript/package.json + refreshed package-lock.json.
     • clients/swift/VERSION.
     • clients/go/VERSION.
   • Regenerates every clients/<lang>/release-metadata.json.

2. chore: bump PROTOCOL_VERSION to 0.4.0 for ongoing development — post-release bump.

   • PROTOCOL_VERSION → 0.4.0; SUPPORTED_PROTOCOL_VERSIONS → ['0.4.0', '0.3.0'].
   • Reopens ## [Unreleased] in every CHANGELOG (and a ## [0.4.0] — Unreleased placeholder in the root spec CHANGELOG).
   • Regenerates per-client Version.generated.* files and release-metadata.json.

Release tags (to push after this PR squash-merges)

The auto-merge is squash, which means commit 1's SHA only survives if a ref points at it. Push all six tags at the original SHA b639a27 (still reachable from the branch until the merge — once tagged, the commit is permanently retained):

RELEASE_SHA=b639a27ee048c77bc262889d813db2295623e425
git tag spec/v0.3.0        $RELEASE_SHA
git tag rust/v0.3.0        $RELEASE_SHA
git tag kotlin/v0.3.0      $RELEASE_SHA
git tag typescript/v0.3.0  $RELEASE_SHA
git tag v0.3.0             $RELEASE_SHA   # Swift (bare per RELEASING.md)
git tag clients/go/v0.3.0  $RELEASE_SHA
git push origin spec/v0.3.0 rust/v0.3.0 kotlin/v0.3.0 typescript/v0.3.0 v0.3.0 clients/go/v0.3.0

Each tag's publish workflow re-validates PROTOCOL_VERSION, the matching CHANGELOG heading, and the native manifest version against the tagged commit, so tags must point at commit 1 (PROTOCOL_VERSION = 0.3.0), not the post-merge HEAD (PROTOCOL_VERSION = 0.4.0).

Artifact	Tag	Publishes to
Spec	spec/v0.3.0	GitHub Release with schema assets
Rust	rust/v0.3.0	crates.io (ahp-types, ahp, ahp-ws)
Kotlin	kotlin/v0.3.0	Maven Central via ADO + ESRP
TypeScript	typescript/v0.3.0	npm via ADO + ESRP
Swift	v0.3.0 (bare)	SwiftPM resolves the tag directly
Go	clients/go/v0.3.0	Go module proxy resolves the tag directly

npm test passes locally after both commits.