fix(rustd): a version bump no longer breaks the workspace it bumps

`make sync-version` rewrote `[workspace.package] version` and exactly one path
dependency's copy of it — afd_core's. The other six still read
`version = "0.26.2"`, which is the requirement `^0.26.2`, so the moment the
workspace version moved to 0.27.0 cargo refused to resolve at all:

    error: failed to select a version for the requirement `afd_auth = "^0.26.2"`
    candidate versions found which didn't match: 0.27.0

`make check-version` grepped for afd_core's line and only afd_core's, so it
printed "✓ all versions match" against a tree that could not build. A gate
reporting green on a broken workspace is worse than no gate.

A `version` on a path dependency only matters when publishing to crates.io.
Nothing here does — the manifest says these crates have no external consumers,
and no workflow runs `cargo publish` — so the key was buying nothing and
costing a release. Removed from all seven, and the two dead lines in
`sync-version`/`check-version` with it.

Verified by doing it: with VERSION at 0.27.0, sync and check both pass and
`cargo metadata` exits 0, where it exited 101 before.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>