feat: support format v4 and bins

[upils]

Chisel is gaining a new release format (v4) and store-backed packages: chisel.yaml
now declares stores:, slice files carry store:/default-track:, and contents:
paths and essential: refs accept a channel: filter (canonical/chisel#299,
upils/chisel#22, upils/chisel#23). Without support for these, the LSP reports
false errors on any release using them.

Two aspects are worth highlighting. First, a store-backed package is known by a
unique prefixed name (default-prefix + package:, e.g. curl → bin-curl),
and that prefix comes from chisel.yaml — so the release file is now parsed,
watched, and any edit to it re-resolves every package name and re-runs
diagnostics. Second, channel: is deliberately not used to narrow collision
or redundancy checks: chisel computes path conflicts irrespective of both
channel: and arch:, and matching that stricter behaviour avoids silently
hiding conflicts that chisel itself rejects.

Note the format also dictates layout: v3 keeps store definitions segregated in
bin-slices/ (so older Chisel never reads the new fields), while v4 places them
in slices/; the index follows the declared format and adjusts its watches when
it changes.