fix: retry short incomplete dflash finals

[OmarB97]

Summary

• Treat short no-tool dflash finals ending on connector tails like and some as incomplete stalls.
• Use the merged stall-retry config helper in the loop so configured retry lanes are honored.
• Allow the retry lane to recover this short-fragment class with either a tool call or completed visible continuation.

Evidence

• python3 -m pytest tests/agent/test_stall_retry.py -q -> 25 passed
• python3 -m py_compile agent/stall_retry.py agent/conversation_loop.py
• Live taro: .venv/bin/python -m pytest tests/agent/test_stall_retry.py -q -> 25 passed
• Live TUI canary returned DETECTOR_OK after verifying the exact screenshot fragment.

Context

Replacement mirror for new work after fork PR #53 was already merged. Upstream PR: NousResearch#35642

[github-actions]

🔎 Lint report: fix/dflash-short-final-fragment-mirror vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 9620 on HEAD, 9620 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 4999 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.