Add failing tests for #1714: agentic sync stall and opaque error handler

[prompt-driven-github]

Summary

Adds failing tests that detect the two bugs reported in #1714.

• 43 tests total: 10 FAIL on current buggy code, 33 PASS on already-correct code
• All 10 failures point directly at the bug locations with actionable assertion messages
• Tests are behavioral (not source-scanning): they invoke real production functions with mocks and verify call arguments at runtime

Test Files

• Unit test: tests/test_issue_1714_sync_stall.py

Root Cause

Bug 1 — Missing timeout= on run_agentic_task() calls:
agentic_sync_identify_modules (pdd/agentic_sync.py:2787) and its sibling agentic_sync_fix_dry_run (pdd/agentic_sync.py:2022) call run_agentic_task() without an explicit timeout= kwarg. When the provider stalls (producing only TUI spinner escape codes), the call blocks for the full DEFAULT_TIMEOUT_SECONDS = 600.0 seconds before returning success=False — confirmed by the session log showing exactly 600.06 s. Same omission exists in agentic_fix.py, agentic_crash.py, agentic_verify.py, agentic_update.py, agentic_test_generate.py, and update_main.py.

Bug 2 — Opaque except Exception handler in sync_main.py:1297:
The per-language exception handler catches all Exceptions but does NOT call record_core_dump_error(), causing pdd_cloud to surface an opaque "An unexpected error occurred during sync" with no exception type, stage name, or traceback. The correct pattern already exists at sync_main.py:821 (budget-exhaustion handler).

What This PR Contains

• Failing unit tests that reproduce both reported bugs
• Tests verified to fail on current code and will pass once the bugs are fixed
• No production code changes — this is a test-only PR to document the bugs

Next Steps

1. Fix Bug 1: Add timeout= kwarg to run_agentic_task() calls in pdd/agentic_sync.py:2787, pdd/agentic_sync.py:2022, and siblings (agentic_fix.py, agentic_crash.py, agentic_verify.py, agentic_update.py, agentic_test_generate.py, update_main.py)
2. Fix Bug 2: Add record_core_dump_error() call with exception type, stage, and traceback to pdd/sync_main.py:1297; surface type(e).__name__ in default rprint output
3. Verify all 43 unit tests pass with the fix: pytest -vv tests/test_issue_1714_sync_stall.py
4. Run full test suite to check for regressions: pytest -vv tests/
5. Mark PR as ready for review

Fixes #1714

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