fix(forge-core): drop -o pipefail from the push script — dash aborts on it (closes #62)

[ALLiDoizCode]

Closes #62. Regression from #61, which I merged — owning the fix.

pushBranch's mint script opened with set -euo pipefail, but sandbox.exec runs through sh -c and the sandbox's /bin/sh is dash. dash has no -o pipefail: it aborts on line 1 with exit 2, so git push never ran. Every CI run has APP_ID/APP_PRIVATE_KEY set, so no agent PR could be opened — the factory has been down since #61 landed at 19:15Z.

Reproduced under the exact shell, both directions

OLD  $ dash -c 'set -euo pipefail; echo reached'
     dash: 1: set: Illegal option -o pipefail          exit 2     ← byte-identical to #62's evidence

NEW  $ dash -c 'set -eu; TOKEN_FILE=$(mktemp); ... '
     LINE 7 REACHED — push would run; mode=600 bytes=11  exit 0

-o pipefail was never load-bearing: the script contains no pipeline. set -eu keeps the fail-fast behaviour, and the dash run above confirms the mode-600 token file and the token round-trip still work. The empty credential.helper= reset — the load-bearing part of #61 — is untouched.

Scope

Fixed both copies reached via sandbox.exec: packages/forge-core/src/sandcastle-runners.ts and .sandcastle/agent-implement-issue.ts.

Not changed: packages/forge-cli/src/stamp.ts's generated verify stub — it carries #!/usr/bin/env bash and is invoked as bash verify/<id>.sh, so pipefail is correct there.

Not propagating: connector's runner has no wrapper script; no other factory repo carries this shape. Checked before assuming.

Test note

pnpm test shows 5 failed files / 6 failed tests — identical on main (runPrGateLadder is not a function, in doctor.test.ts), so pre-existing and unrelated. Flagging separately that Forge's gate passes while those fail, which means the gate is not running the full suite.

How this got in

I reviewed #61's diff and checked the credential handling, which was correct — but I did not check the shell the script runs under. The gate cannot catch it: the push path only executes in-sandbox at runtime.