Support redirects, cat, xargs

Editor assessment

The header is pleasant — feat(task) with a compact list of new shell capabilities ('support redirects, cat, xargs') — but the body is odd: 'feat: upgrade to deno_task_shell 0.4.0' is a second conventional-commit header embedded in the body, likely debris from a squash. It should be prose ('Upgrades deno_task_shell to 0.4.0, which adds these builtins'), both for readability and because changelog parsers that scan for type prefixes can misread such lines. It also reveals the real mechanism is a dependency upgrade, which deserves stating plainly. Header conventions themselves — length, mood, blank-line separation — are all correct.