Tebako Python runtime packages v0.2.7

Tebako Python runtime packages

Release version: v0.2.7

Every runtime package (the interpreter executable + its .tfs env image + the
windows runtime DLL) ships with its own metadata, written once by the build leg that
produced it (spec 13 §2a): the <asset>.sha256 sidecar next to every asset is the
trust anchor (the tebako store's own sidecar shape, spec 00 §8), and the
<package>.manifest.json shard next to every package carries exactly its
release-index entry. On signing-enabled lines every served name also carries its
own detached .asc (spec 09 §5).

There is no monolithic manifest.json / SHA256SUMS.txt release asset: both are
derivable conveniences, computed consumer-side from the shards + the asset listing.
The machine-readable resolution index is the publishing repo's
tpkg-registry.yaml (spec 04 §2).