IRIX 7 v0.1.3

Native Indy update. This is a native-only release; the Wasm/mesh line is not
claimed and M1/M2 remain in progress.

Highlights

HACS-style package index at packages/, with digest-pinned modules and a
static Rust std userland image.
sash can list the index, verify and load a module, and inspect an EROFS
image over HTTPS Range.
The primary boot path works with no SCSI disk: DHCP and GitHub autoload bring
up the network, and package discovery/install succeed entirely from RAM.
SCSI is optional. The idle write-cache design is documented as a module that
drains a SHA-256-keyed RAM queue into a cache-owned target; it is not a boot
prerequisite.
The PROM is 520,840 of 524,288 bytes; CI enforces the limit.

Diskless IRIS boot: no SCSI target, network up, packages lists the index,
packages install logical verifies and runs with cap=ok.
Remote EROFS inspection over HTTP Range.
cargo fmt, clippy, workspace tests, cross-build, ROM build, actionlint and
mdbook.