iyi 0.12.0

A Crystal project becomes iyi modules, and the thing people download
carries the library it names. iyi migrate writes a checkout out as
iyi — a whole project, or one file at a time beside its source — and it
was written against twelve real projects taken as they come from GitHub,
crystal-db, shards, halite, ameba, amber and Kemal's own among
them, which is where five of its rules came from. iyi bind puts every
shard under lib/ behind a boundary a program imports, and the sixteen
defects in that boundary were found the same way: by consuming one. The
tarball this release publishes is also the first to carry
share/iyi/src/std, so import std/text resolves out of an install
rather than answering "can't find module", and the first to publish
SHA256SUMS beside the tarballs, which install.sh checks before it
unpacks anything.

A server survives its own collector. Two runtime mistakes of one
shape — a heap pointer held as a number, where the collector is precise
over a typed object's fields, and a fiber's stack mapped and never handed
back — took a kemal port down at request ~400 under wrk -c 100 -d 10.
The same program now serves 237,066 requests at 23,705/s behind 299
mappings and 14 MB flat, and the stack pool's link moved to a word that
is writable where a page is 16 KiB. The editor holds too: ▶ run no
longer ends the session, a workspace pull reads its inbox between files
(a hover behind a 94-file walk: 10.9 s to 0.23 s), and a panic that could
not be printed is a sentence on descriptor 2 instead of a segfault.

Around those: socket and format are src/std/ modules, so a program
that imports neither carries neither and the prelude is back under its
ceiling; iyi migrate --annotate writes the types R-2 wants off the
Crystal the tree already compiles; R-4 is measured rather than asserted;
the agent loop runs iyi fix before it asks the model again; and two
samples keep state across runs, one remembering what it has seen and one
forgetting it on a clock.

.iyimod is v49. See CHANGELOG.md for the rest.