Replace our nix32 encoder with harmonia-utils-base-encoding's base32 and
the hand-walked serde_json::Value of the caches' .ls listings with
harmonia-file-core's FileTree, which is the serde model of Nix's file
system object JSON. Both are pure crates (data-encoding/derive_more,
serde/serde_json/thiserror), pulled as a git dependency pinned to
harmonia 3edb37ae: only harmonia-utils-hash and harmonia-store-core exist
on crates.io, as 0.0.0-alpha.0 placeholders. A listing node without
"size" (regular) or "entries" (directory) is now an error instead of
being read as 0 / empty; Nix always writes both.

Kept ours:
- NAR unpacking: harmonia-file-nar is a tokio AsyncRead parser/restorer;
we unpack synchronously from the blocking HTTP/decompressor stream
while hashing, in a sync FUSE daemon.
- narinfo parsing, store path names and NarHash parsing:
harmonia-store-nar-info, -store-path and -utils-hash all pull in
aws-lc-rs (aws-lc-sys C build), blake3 and md5, nar-info also
ed25519-dalek and getrandom: +43 crates for ~15 lines. closure also
passes the narinfo text through verbatim, and harmonia's parser
rejects whole narinfos for fields we don't use (Sig, CA, FileHash).
- The in-memory Tree: matching FileTree(FileSystemObject::Regular(
Regular { .. })) in lazy.rs is clumsier than our flat enum.

Incident 2026-10-17: radio→styx UDP was blackholed for ~40 min after a
sendto() hit ENETUNREACH; tincd never recovered the UDP path on its own.
The fix is upstream as Mic92/tincr#140.

The fork is rebased onto upstream Mic92/tincr main: 6 of the 8 commits on
lassulus/fixes are upstream now, leaving the tunnel-address gate and the
ENETUNREACH fix on lassulus/fixes-rebased (bfcbbc69).

pkgs/tincr pins the same branch and is what every machine runs (the flake
input only provides barnacle's darwin module), so bump it and its update
script along with the input.

RUST_LOG=tinc=warn hid every routing/relay event, so path problems were
only visible over SSH. Enable Info for tincd::graph (became
reachable/unreachable via X), tincd::conn (meta connections up/down) and
tincd::net (key exchange, UDP idle revalidation/timeouts, PMTU
fixed/increase/decrease). Their Debug/Trace stays off because tincd::net
and tincd::proto log per packet there; tincd (autoconnect), tincd::auth
and tincd::proto Info stay off as redundant.

Expected volume is roughly 100-250 lines/h on a hub like neoprism and
30-60/h on leaves, plus autoconnect dial attempts to dead hosts in conn.

iets (numtide/iets, a Nix evaluator in Rust) gives the same drvPath,
isCached and cacheStatus for every machine as nix-eval-jobs 2.35.4, in
24-35s instead of 108-144s (4 workers, coaxmetal). It is a flake input
so CI builds it once and pushes it to cache.lassul.us with niks3 and
the lazy store.

Reading the lock file from the fetched src is import from derivation:
every evaluation of the machines that have it (aergia, green, ignavia,
mors) fetches the source first, and evaluators without IFD (iets) fail
on them.

Account linking is off: byoidc never marks emails verified and anyone can
run a provider claiming any address. New users are created automatically.