fix: apply fixed_base_score repo override on issue-discovery cache-miss path (#1172)

[alpurkan17]

Summary

PR #1115 introduced RepositoryConfig.fixed_base_score to decouple PR base scoring from token math for configured repos. The override is applied correctly in OSS scoring (score_mirror_pr) but was missing on the issue-discovery cache-miss path (_resolve_solving_pr_score).

On a cache miss (typical when the solver is a non-miner contributor), the solving PR's base_score was computed purely from tokenized files, ignoring repo_config.fixed_base_score. This meant two miners filing equivalent issues in the same fixed_base_score repo could receive different discovery base scores depending on whether their issue was solved by a registered miner (cache hit → override applied) or an outside contributor (cache miss → override skipped).

This fix threads mirror_repos into _resolve_solving_pr_score and applies the same fixed_base_score override that OSS scoring uses, so discovery_base_score is consistent regardless of solver identity.

Validation

• mirror_repos (already available in the caller _score_miner_mirror_issues) is passed to _resolve_solving_pr_score as a new parameter
• After token computation in the cache-miss path, repo_config.fixed_base_score is applied if present (matching score_mirror_pr at scoring.py L164–L167)
• Token fields remain token-derived (unchanged behavior, matching the legacy-parity comment)
• ruff check + ruff format pass

Closes #1172

[anderdc]

Tighten the signature — the function only ever looks one repo up, so passing the whole dict is more than it needs.

Change _resolve_solving_pr_score to take repo_config: Optional[RepositoryConfig] (or just fixed_base_score: Optional[float]) instead of mirror_repos: Dict[str, RepositoryConfig]. The caller _score_miner_mirror_issues already resolves repo_config = mirror_repos.get(issue.repo_full_name) at scan.py:419 — hoist that lookup above the call and pass the resolved value. The override branch inside the function then just checks the passed-in config directly.

Behavior is correct as-is; this is purely a signature cleanup so the helper stops knowing about the full config map.

[alpurkan17]

Fixed per review: hoisted repo_config lookup to caller, signature now takes repo_config: Optional[RepositoryConfig] instead of the full mirror_repos dict.

[alpurkan17]

Thank you for the review @anderdc! Glad to contribute. 🚀