fix(send): retain diagnostics and fail exit status for failed execution

[adrianwebb]

Outcome

A failed send receipt no longer reports success to callers. Fixes #189.

Work authority

• Work item / Issue: Return nonzero with retained diagnostics when waited send fails #189; Diagnose and repair repeated send failures after Terra activation deployment#693
• Proposal / decision: Distinguish HTTP success from agent execution success.
• Assignment / checkpoint: User-requested send reliability repair.
• Actor: adrianwebb
• Human authority: User requested fixing ordinary CLI sends.
• Agent / capacity provider: Codex desktop under user authority.
• Exact base ref: 918b8b5
• Exact head ref: 1253402
• Agent-authored under human authority

Plan

Recognize failed terminal send receipts at the common command boundary; keep receipt diagnostics and return nonzero; test successful and failed cases.

Changes and commits

cc8bd0d adds terminal status handling and two regression tests.

Verification

Two focused command-boundary tests passed. Managed CLI generation 8 activated; Actions pending. 1253402 groups the test by communication ownership.

Risk and rollback

No schema, API contract, or credential changes. Only failed sends change exit status. Revert CLI source through managed development if required.

Completion summary

Bounded implementation complete; Actions and activation remain gates. This does not claim to repair the underlying sandbox failure.

Submission checklist

• The change is bounded to the stated work item and target repository.
• Exact base and head refs are recorded and the branch is ready for review.
• Verification and compatibility evidence are recorded above.
• No plaintext secrets, credentials, machine state, or unrelated residue are included.
• Plan, status, commits, and completion summary form a complete durable record.
• Rollback or recovery steps are documented and executable.