fix(query): extend auto-fetch fallback to summarizePr and summarizeDiff

Apply EnsureRef to the two other user-facing base-ref callers so they
work in shallow CI clones just like review. summarizeDiff uses
best-effort resolution since its inputs can be raw SHAs, which should
not go through branch-name fetch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: SimplyLiz

internal/query/navigation.go

@@ -2026,6 +2026,12 @@ func (e *Engine) SummarizeDiff(ctx context.Context, opts SummarizeDiffOptions) (
 		selector = DiffSelector{Type: "commitRange", Value: opts.CommitRange.Base + ".." + opts.CommitRange.Head}
 		base = opts.CommitRange.Base
 		head = opts.CommitRange.Head
+		if resolved, rerr := e.gitAdapter.EnsureRef(base); rerr == nil {
+			base = resolved
+		}
+		if resolved, rerr := e.gitAdapter.EnsureRef(head); rerr == nil {
+			head = resolved
+		}
 		diffStats, err = e.gitAdapter.GetCommitRangeDiff(base, head)
 		if err != nil {
 			return nil, fmt.Errorf("failed to get commit range diff: %w", err)

internal/query/pr.go

@@ -102,7 +102,12 @@ func (e *Engine) SummarizePR(ctx context.Context, opts SummarizePROptions) (*Sum
 	if headRef == "" {
 		headRef = "HEAD"
 	}
-	diffStats, err := e.gitAdapter.GetCommitRangeDiff(opts.BaseBranch, headRef)
+	baseRef, err := e.gitAdapter.EnsureRef(opts.BaseBranch)
+	if err != nil {
+		return nil, fmt.Errorf("failed to resolve base ref %q: %w", opts.BaseBranch, err)
+	}
+	opts.BaseBranch = baseRef
+	diffStats, err := e.gitAdapter.GetCommitRangeDiff(baseRef, headRef)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get diff: %w", err)
 	}