Make tail-rec optimization improvements

[LPTK]

• Run TailRecOpt both before and after simplification so annotations are checked early while later optimization opportunities exposed by simplifications can still be rewritten.
• Add a checkAnnotations mode to suppress duplicate/spurious annotation diagnostics on the second TailRecOpt run.
• Fix TailRecOpt’s call graph so under-applied curried calls are not treated as executable recursive call edges.
• Add/update regression coverage for multi-argument-list tail recursion, including the partial-application case that previously caused the second pass to reprocess already optimized code.
• Refresh affected golden outputs, including Runtime.mjs.

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Codex was used to help diagnose issues and change code, but the design was mine (the fixes proposed by Codex were all stupid workarounds eschewing the real issue).

[Copilot]

Pull request overview

This PR refines the HKMC2 tail-recursion optimization pipeline by running TailRecOpt twice (pre/post simplification), improving annotation checking behavior, and fixing call-graph construction so under-applied curried calls are not treated as executable recursion edges. It also updates/extends regression coverage around multi-argument-list tail recursion and refreshes the associated golden outputs (including runtime snapshots).

Changes:

• Run TailRecOpt both before and after simplification, with a new checkAnnotations mode to avoid duplicate/spurious diagnostics on the second run.
• Correct TailRecOpt call-graph edge construction to ignore under-applied curried calls (closure construction) as recursion edges.
• Update/add regression tests and golden outputs for tailrec + currying + partial-application scenarios, plus refreshed IR/JS snapshots.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
hkmc2/shared/src/main/scala/hkmc2/codegen/TailRecOpt.scala	Adds checkAnnotations mode and refines call-graph edge detection to require exact saturation for executable edges/jumps.
hkmc2/shared/src/main/scala/hkmc2/codegen/CompilationPipeline.scala	Runs TailRecOpt twice (checked early, then optimization-only later) to capture post-simplification opportunities.
hkmc2/shared/src/main/scala/hkmc2/codegen/Block.scala	Makes Call equality/hash include metadata so annotations like @tailcall aren’t ignored.
hkmc2/shared/src/test/mlscript/tailrec/TailRecOpt.mls	Updates snapshots to :soir and refreshes expected optimized IR/errors.
hkmc2/shared/src/test/mlscript/tailrec/Simple.mls	Updates warning text and refreshes JS snapshot for a non-tail-recursive nested self-call case.
hkmc2/shared/src/test/mlscript/tailrec/MultiArgLists.mls	Adds/updates regression coverage for multi-arg-list tail recursion, including the partial-application edge case.
hkmc2/shared/src/test/mlscript/tailrec/Errors.mls	Updates warning text expectations and adds new warning/error cases for @tailrec.
hkmc2/shared/src/test/mlscript/tailrec/Annots.mls	Updates warning text expectation for @tailrec with no tail calls.
hkmc2/shared/src/test/mlscript/deforest/eta-expansion/recursive.mls	Refreshes optimized IR snapshot (loopification visible post pipeline changes).
hkmc2/shared/src/test/mlscript/deforest/cyclic.mls	Refreshes optimized IR snapshot reflecting loopified worker behavior.
hkmc2/shared/src/test/mlscript/codegen/TailRecFormerFailure.mls	Refreshes optimized IR snapshots for former tailrec failure cases.
hkmc2/shared/src/test/mlscript/codegen/ConfigDirective.mls	Refreshes optimized IR snapshots and updates directives to :soir.
hkmc2/shared/src/test/mlscript-compile/Runtime.mls	Updates runtime source to use unreachable in a way consistent with generated JS.
hkmc2/shared/src/test/mlscript-compile/Runtime.mjs	Refreshes generated runtime snapshot (notably inlining loop structure into separate methods).

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[CAG2Mark]

Just one small comment about the error message.