fix(repo): use tsx fallback on Node 26+ for NODE_OPTIONS

[gabroberge]

Summary

• ark/repo/nodeOptions.js: From Node 26 onward, --experimental-transform-types is not allowed in NODE_OPTIONS, so any node child process started after addNodeDevOptions() could fail with: --experimental-transform-types is not allowed in NODE_OPTIONS.
• Version gate is tightened to (major > 22 && major < 26) || (major === 22 && minor >= 7) so 26+ uses the --import tsx fallback (same broad approach as pre–22.7).
• Refactor: flag selection lives in versionedFlagsFor(major, minor); the fallback path logs getFallbackReason(major) (distinct copy for 26+ vs other fallback cases) then returns "--import tsx".

Test plan

• pnpm build on Node 26+ (or rely on CI compatibility (ubuntu-latest, latest))
• Optional smoke: Node 22 / 24 still uses --experimental-transform-types --no-warnings

Note

Scope: minimal fix so CI passes on Node 26+; not a broader build refactor.

I’m not asserting we should keep tsx for Node ≥ 26 forever—only that it unblocks today’s NODE_OPTIONS restriction. Maintainers can propose a native or alternative approach when they see fit.

[pullfrog]

No new issues found.

TL;DR — Gates --experimental-transform-types to Node 22.7 through 25.x and falls back to --import tsx on Node 26+, where the flag was removed and is rejected inside NODE_OPTIONS.

Key changes

• Cap experimental-transform-types at Node 25 — predicate is now (major > 22 && major < 26) || (major === 22 && minor >= 7), so Node 26+ takes the tsx fallback path.
• Extract versionedFlagsFor(major, minor) — flag selection moves out of the top-level ternary into a named function, with a sibling getFallbackReason(major) that emits distinct copy for the 26+ case vs the pre-22.7 case.

_{Summary ｜ 1 file ｜ 1 commit ｜ base: main ← ci/node-26-node-options}

Node 26 removes --experimental-transform-types

Before: addNodeDevOptions() injected --experimental-transform-types --no-warnings into NODE_OPTIONS for any major > 22, so child node processes on Node 26+ aborted with --experimental-transform-types is not allowed in NODE_OPTIONS.
After: Node 26+ logs a fallback reason and uses --import tsx instead, matching the pre-22.7 fallback shape.

Verified against the Node v26.1.0 TypeScript docs: the v26.0.0 history entry reads "Removed --experimental-transform-types flag." Type stripping itself remains on by default in 26, but the transform flag is gone — passing it via NODE_OPTIONS is what triggers the error this PR avoids. The single consumer is ark/repo/ts.js, which calls addNodeDevOptions() before spawning a node child via execSync, so the fix lands exactly where it needs to.

ark/repo/nodeOptions.js

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