fix(terminal): preserve partial output when command times out

[teknium1]

When a command timed out in _execute_oneshot, all captured output was discarded — the agent only saw Command timed out after Xs with zero context about what happened. For long builds or test runs, this meant no way to tell which tests passed or where it failed.

The interrupt path (user sends a new message) already preserves partial output. The timeout path wasn't doing the same thing.

E2E verified:

• echo line1 && echo line2 && sleep 30 (timeout=2) → all lines captured + timeout marker ✅
• sleep 30 (timeout=1) → clean timeout message, no leading newline ✅
• 50-line output + sleep → all lines preserved + timeout marker ✅

Includes 2 regression tests from the original PR.

Salvaged from PR #3286 by @binhnt92 with authorship preserved.

[github-actions]

⚠️ Supply Chain Risk Detected

This PR contains patterns commonly associated with supply chain attacks. This does not mean the PR is malicious — but these patterns require careful human review before merging.

⚠️ WARNING: Install hook files modified

These files can execute code during package installation or interpreter startup.

Files:

hermes_cli/setup.py

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