fix(pixi): repair multi-line cmake task commands broken by pixi 0.70

[thewtex]

Summary

Repairs the multi-line cmake task commands in the pixi manifests, which recently began failing the Native C++ CI workflow with exit code 127. The same broken pattern was also fixed in the create-itk-wasm project generator (so newly scaffolded projects are not born broken) and guarded with a regression test.

Fixes the failure seen in Native C++ run #27805452478.

Root cause

Recent pixi (≥ 0.70, which switched its task runner to deno_task_shell) treats a bare newline inside a multi-line cmd string as a command terminator. The configure-itk* cmake tasks laid out their flags one-per-line with no continuation token:

cmd = '''cmake -B$ITK_WASM_ITK_BUILD_DIR -S$ITK_WASM_ITK_SOURCE_DIR -GNinja
  -DCMAKE_CXX_STANDARD:STRING=20
  -DCMAKE_BUILD_TYPE:STRING=Debug
  ...'''

Under the new parser, only cmake … -GNinja ran (configuring ITK with default flags), and every subsequent -D… line was executed as its own command, producing -DCMAKE_CXX_STANDARD:STRING=20: command not found for each flag and ultimately exit code 127. This was reproduced locally with pixi 0.70.1.

Changes

• pixi.toml — Added a trailing \ line continuation to every wrapped line of the configure-itk, configure-itk-wasm, and ten configure-native-* cmake tasks, so all -D flags are passed to a single cmake invocation. Layout and behavior are otherwise unchanged.
• packages/core/typescript/create-itk-wasm/src/generate/pixi-toml.ts — The scaffolding generator emitted the same broken pattern in its configure-itk, configure-itk-wasm, and configure-native tasks, so every generated project would break identically under pixi ≥ 0.70. Applied the same \ continuation fix in the template literal.
• packages/core/typescript/create-itk-wasm/src/test-pixi-toml.ts (new) — Regression test that runs the real generatePixiToml into a temp directory and asserts that every line of each multi-line cmd (except the last) ends with a shell continuation token (\, &&, ||, |, &). Wired into the package's test script as test:pixiToml.
• pixi.lock — Upgraded from lockfile format v6 → v7 via pixi lock to clear the pixi install format warning. Re-solved from locked content only; the resolved package set is identical (534 packages, none added or removed).

Implementation notes

• In the TypeScript generator the continuation is written as \\ within the JS template literal, which emits a literal backslash + newline into the generated pixi.toml — verified the output matches the hand-fixed root manifest.
• Package-level packages/*/pixi.toml manifests were checked and left unchanged: their multi-line commands already terminate each line with &&, which the new parser continues correctly.

Testing

• pnpm --filter create-itk-wasm build then test:pixiToml passes (15 multi-line commands checked).
• Confirmed the test is a genuine guard: reverting the generator fix makes it fail with an actionable list of offending lines; restoring it passes.
• CodeRabbit review of the changes: 0 findings.
• pixi install --locked and pixi list --locked run clean with no format warning.

🤖 Generated with Claude Code