voxora-cli and voxora-testkit CHANGELOG.md are missing the 0.4.2 entry

## What

`voxora-cli/CHANGELOG.md` and `voxora-testkit/CHANGELOG.md`
both stop at `## [0.4.0] — 2026-09-03` even though `cargo
metadata` reports both crates at version `0.4.2` (the
`version.workspace = true` inheritance advanced the number
when EPIC #100 / PR #105 bumped the coordinated version). The
other nine publishable crates all gained an `## [0.4.2] —
2026-09-05` entry under EPIC #100; only these two `publish =
false` crates are missing it.

AGENTS.md § "Version coordination" instructs that every
participating workspace crate ships at the coordinated version,
and the CHANGELOG is the audit trail. The current state is
internally inconsistent: a reader sees "0.4.2" in the
manifest, "0.4.0" in the CHANGELOG, and "0.4.2" in
`cargo metadata`. The publish=false carve-out is real (the
crates do not ship to crates.io), but the version still
matters for any consumer who reads the source tree directly or
who pins `voxora-cli` to an exact version in a downstream
`Cargo.toml`.

## Recipe

Add a `## [0.4.2] — 2026-09-05` section to both
`voxora-cli/CHANGELOG.md` and `voxora-testkit/CHANGELOG.md`.
The entry should record the coordinated 0.4.2 release (no public
API change, MSRV bump from 1.86 to 1.88, EPIC #100 CI hardening
backports). The same rationale is already in the other nine
CHANGELOGs; the wording can mirror that of
`voxora-traits/CHANGELOG.md:75-90`.

## Acceptance

- `voxora-cli/CHANGELOG.md` and `voxora-testkit/CHANGELOG.md`
both contain a `## [0.4.2] — 2026-09-05` section.
- The `## [Unreleased]` section in each remains ready for the
next coordinated bump.