chore: prepare dhttp v0.5.0-beta.2

[eareimu]

Release prep

Prepare dhttp v0.5.0-beta.2, including npm/PyPI package metadata, and update h3x/dyns dependency contracts to beta.2.

Draft tag message

# dhttp v0.5.0-beta.2

## Changes

- Keep endpoint candidate resolvers available through the endpoint-facing DHTTP stack.
- Update `h3x` and `dyns` dependency contracts for the beta.2 line.
- Align npm and PyPI package metadata with the v0.5.0-beta.2 release.

## Published surfaces

- crates.io: `dhttp` v0.5.0-beta.2
- npm: `@genmeta/dhttp` v0.5.0-beta.2
- PyPI: `dhttpy` v0.5.0b2

Release gates

• Target branch: main
• Planned tag: v0.5.0-beta.2
• Initial/incremental: incremental
• Surfaces: crates.io, npm @genmeta/dhttp, PyPI dhttpy, tag-CI GitHub Release

Dependency wait conditions

Wait for h3x v0.6.0-beta.2 and dyns v0.6.0-beta.2 to be published and visible on crates.io before final merge/tag readiness.