Extends the test-setup git hardening. The engine --shard=2/2 worktree-heavy
reliability suite was hanging in CI (progressing healthily, then ~2 min of
silence before the job timeout killed it with no test failure) — the signature
of a git command blocking on an interactive prompt. A dev macOS git config
suppresses these; a bare Linux CI git does not. Disable terminal credential
prompts (GIT_TERMINAL_PROMPT=0), the editor (GIT_EDITOR=true), and the pager
(GIT_PAGER=cat) for every test process so no git invocation can block on a TTY.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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