Chunked review: summary footer says 'No issues found across all chunks' even when issues were found

[ajianaz]

What

In chunked review mode (--max-diff-size), the merged report can print a contradictory footer: the header says Found 1 issue: ... ⚠ BLOCKED while the summary footer says No issues found across all chunks. — in the same output.

Live evidence: codecoradev/gaira PR #108, cora-review verdict comment for run #1388 (2026-10-04): "Found 1 issue: 0 critical 1 major" + "⚠ BLOCKED" + "No issues found across all chunks."

Why

src/commands/review.rs (chunked merge path): the merged_summary fallback keys only off summaries.is_empty() and any_error. Chunks that RETURN issues but with an empty summary field push nothing into summaries, so the no-findings fallback fires even though all_issues is non-empty.

Suggested fix

Make the fallback consult all_issues first:

let merged_summary = if summaries.is_empty() {
    if !all_issues.is_empty() {
        format!("{} issue(s) found across chunks.", all_issues.len())
    } else if any_error {
        "Review completed with partial results (some chunks failed).".to_string()
    } else {
        "No issues found across all chunks.".to_string()
    }
} else {
    summaries.join("\n\n")
};

Gating is unaffected (exit code derives from should_block, which was correct in the live case) — this is report text only. Repro: any diff above --max-diff-size where the model returns issues with empty per-chunk summaries.