Move Bifrost to ShenOSKernel 42.2

[pyrex41]

Summary

Every port Bifrost drives now runs the community ShenOSKernel 42.2: Shen-Language/shen-sources tag shen-42.2, commit 73507e069fe147aefb728d632c4ce40bc6a7b314, SHA-256 1d02273003654d34ec020ae67cb214ecec410dee3350419ff807d82b652678d8. This is lineage option (a): 42.2 replaces Tarver S42.0 wholesale. This PR moves the corpus, adapters and docs to 42.2, adds cases for the 42.1/42.2 behaviour changes, and makes the kernel-split cases hard agreements again.

Port PRs:

• Merge upstream shen-scheme 0.50: adopt ShenOSKernel 42.2 wholesale shen-scheme#9, Upgrade kernel to ShenOSKernel 42.2 (community lineage, shen-scheme 0.50 parity) shen-go#62, Upgrade kernel to ShenOSKernel 42.2 (shen-scheme 0.50 parity) shen-cl#22, Upgrade kernel to ShenOSKernel 42.2 (shen-scheme 0.50 parity) ShenScript#15
• Upgrade kernel to ShenOSKernel 42.2 (shen-scheme 0.50 parity) shen-lua#81, Upgrade to ShenOSKernel 42.2 (community kernel, booted through shen.initialise) shen-c#1, Upgrade kernel to ShenOSKernel 42.2 (shen-scheme 0.50 parity) shen-rust#29, Upgrade kernel to ShenOSKernel 42.2 (shen-scheme 0.50 parity) shen-julia#11
• Boot ShenOSKernel 42.2 (community shen-sources, matching shen-scheme 0.50) shen-erl#5, Move subset baseline and differential reference to ShenOSKernel 42.2 (shen-scheme 0.50) shen-joy#2, Upgrade to ShenOSKernel 42.2 (shen-scheme 0.50 kernel) shen-truffle#6
• shen-swift: branch ready locally, not yet pushed.

Changes

Corpus

• version-expr-42 is renamed version-expr-42.2 (golden 42.2); version-banner-contains now looks for 42.2.
• error-message-head is a pinned golden again: head expects a non-empty list.
• New cases/kernel-42.json:
  • lineread-eof-no-newline and read-eof-no-newline read from a file stream, not REPL stdin, because upstream 0.50's REPL hangs at EOF.
  • source-form-before-macros: a handler and a macro rule share the same head. The result shows the handler ran first and the macro then expanded its output.
  • namespace-externals-expression: (externals (fn-call)), a capability SKIP where namespaces aren't booted.
• Integer precision is a documented divergence with a per-port bucket table: bigint-2pow53-plus-1 and bigint-2pow63-ordered.
  • Only shen-cl, shen-erl and shen-scheme are true bignums.
  • shen-c and shen-julia wrap at 2^63.
  • shen-rust, shen-swift and shen-truffle overflow to a double.
  • shen-go, ShenScript and shen-lua are IEEE doubles.
• load-toplevel-echo is a hard agreement. Its doc said the normaliser drops the blank line before the run time: banner, but the code never did; it now does.

Harness

• A BIFROST-SKIP: output line counts as a capability SKIP, the same as exit 3, since Shen has no portable exit.
• A known_divergence case can carry a table pinning each port to its bucket; a port that changes bucket is a FAIL.
• The normaliser drops JVM Picked up JAVA_TOOL_OPTIONS/_JAVA_OPTIONS/JDK_JAVA_OPTIONS: lines, so shen-truffle passes with a proxy-set JAVA_TOOL_OPTIONS.
• Captured output is capped at 8 MB (upstream 0.50's REPL prints about 5 MB/s at EOF).
• impls --versions reads the leading kernel token of the banner, and falls back to (version) for port-local banners such as shen-c's Shen-C 0.2.3.
• evaluateCase is split into run and judgeCase.
• New tests: version parsing, normaliser, skip marker, bucket table.

Adapters

• kernel is 42.2 everywhere; shen-joy is bounded-42.2-subset.
• shen-scheme:
  • Defaults to git-build of the pyrex41 fork (upstream v0.50 merged, plus the EOF and *hush* fixes), using the upstream CI steps: fetch-kernel, fetch-prebuilt, precompile-with-prebuilt, all. The old make all could not build from a fresh clone.
  • brew is documented as not a 42.2 route: homebrew-core has no shen-scheme formula, and the Shen-Language tap ships 0.17.
  • The note now describes 0.50's layout: petite.boot + scheme.boot + lib/shen-scheme/shen-scheme/runtime.so, overridable with $SHEN_SCHEME_HOME.
• Notes updated for shen-julia (42.2 banner, ~5 s start-up), shen-swift (16 modules plus shen.initialise, ~0.5 s boot, 143/143, native launcher, --stdlib), shen-erl (no unzip), shen-cl (scripts/fetch-kernel.sh), shen-truffle (JDK 23+, JVM notice) and shen-c (boot sequence and known gaps).
• shen-joy: the shake expectation is programs/joy-sum.shen → 32004000; tests/fib.shen is a capability SKIP.
• shen-go v1.5.0 and shen-lua v0.11.0 / 0.11.0-1 pins are unchanged, with a TODO: no 42.2 releases exist yet. Use --ref kernel-42.2 until they do.
• .gitignore covers shen-lua's .stlib cache; .gitattributes keeps the EOF fixtures byte-exact.

Docs

• docs/matrix.md: kernel, capability SKIP, precision table, upstream-reference notes, known port gaps, normaliser and joy shake.
• Also updated: docs/install.md, docs/cli.md, docs/port-layout.md, README.md.

Verification

• go vet ./... && go test ./...: ok.
• bifrost --impls shen-cl,shen-go,shen-erl,shen-lua,ShenScript,shen-scheme,shen-julia,shen-c,shen-rust,shen-swift,shen-truffle, with every port on kernel-42.2 and shen-scheme as the fork built from shake: add scheme (shen-scheme) target #9: 64 pass, 2 diverge (known), 6 FAIL.
  • 62 of 72 cases pass on every port.
  • namespace-externals-expression passes on shen-scheme and shen-rust and is SKIP elsewhere.
  • Both DIVERGE cases are the integer-precision buckets, and every port is in its tabled bucket.

case	FAILing port	cause (already present on the port's S42.0 main branch)
float-add-imprecise	shen-c	prints 0.3
version-banner-contains	shen-c	banner is Shen-C 0.2.3
bounded-tail-sum-file	shen-c	script mode echoes toplevel values (not quiet-load)
source-form-before-macros	shen-c	same script echo; the value itself is correct
integer-float-integral	shen-julia	native integer? is false for 4.0
hash-agrees-with-equality	shen-julia	hash 1 ≠ hash 1.0

• Upstream reference: BIFROST_SHEN_SCHEME=<shen-scheme 0.50> bifrost --impls shen-scheme,shen-cl,shen-go,shen-rust gives 68 pass, 2 diverge, 2 FAIL. The two FAILs are exactly hush-file-write (upstream writes 0 bytes under -q) and stdin-eof-clean-exit (the upstream REPL loops). Both are intended and documented.
• bifrost impls --versions: all 11 installed ports report 42.2, including shen-c through the (version) fallback, and upstream 0.50.
• bifrost --heavy --only yggdrasil-shake-parity with a Yggdrasil kernel-42.2 build (shen-julia skipped as a host by default): kernel.kl + manifest are byte-identical across shen-cl, shen-go, shen-erl, shen-rust, shen-lua, ShenScript, shen-scheme, shen-swift and shen-truffle. shen-c FAILs: as a host it loads Yggdrasil but writes no kernel.kl.

Remaining work / known failures

• New shen-go and shen-lua releases on 42.2 (tag + rock), then move the pins.
• shen-c: standard --version banner, quiet script mode, float printing, and the Yggdrasil host producing no kernel.kl.
• shen-julia: integer? on integral floats, and hash agreeing with =.
• Merge the port PRs; until then, git-build installs need --ref kernel-42.2.
• shen-joy launcher not built here; shen-swift not pushed yet.
• --heavy is not fully green while shen-c is included.

Refs #26

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https://claude.ai/code/session_01X718xocsFckMvso6EAKoXR

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