fix: retry a feedback setup failure instead of ending the run (#164)

[mohammadp1001]

Fixes #164.

FR-016a says a failed evaluation is retried up to 3 times and then marked failed, which
unblocks the ticker, and the run carries on. Two steps ran before the retry loop and
got none of that protection: reading the entry report and fetching the evaluation price.

Both touch the outside world, so a missing report file or an unreachable Alpaca raised
straight out of evaluate(), travelled up through _process_session and stopped the whole
run - leaving the position blocked forever, which is exactly what FR-016a and FR-017 exist
to prevent.

This is not a hypothetical path. The entry session may legitimately carry no report path;
_run_feedback already passes html_report_path or "" for that case, so _extract_thesis
opening "" and raising FileNotFoundError is a path the code expects to reach.

What changed

• The thesis read and the price fetch moved inside the retry loop, so they are retried
  like any other failure and, after 3 attempts, end in the normal EVALUATION_FAILED path
  that unblocks the ticker.
• _write_failure now works when no price was ever fetched. candle_close_price is
  NOT NULL, so the position's own exit price stands in - a real price for this position -
  and the reasoning text records that the evaluation price could not be fetched, so the row
  is not mistaken for a genuine candle close.
• Scheduler._run_feedback wraps each position. One that still blows up is logged, echoed,
  and emitted as EVALUATION_FAILED, and the loop moves on to the next position and to the
  session.

Tests

Nine added. Five of them fail against the old code:

• test_a_missing_report_file_does_not_escape_evaluate
• test_a_price_fetch_failure_does_not_escape_evaluate
• test_a_price_fetch_is_retried_three_times
• test_a_price_fetch_that_recovers_on_the_second_attempt_succeeds
• test_failure_without_a_price_records_the_exit_price_instead

The rest pin the scheduler safety net and confirm a successful price fetch is still the
price recorded on an LLM-side failure.

Verification

603 passed in 137.73s (0:02:17)
Required test coverage of 100% reached. Total coverage: 100.00%
ruff check alphoryn/ tests/ -> All checks passed!