fix(capture): drop unused err param in SVG rasterize catch block

oxlint flagged `catch (err)` after the SVG→PNG sharp fix. The catch
intentionally swallows (sharp can fail on exotic SVG features and the
contact sheet remains the authoritative fallback). Switch to bare
`catch {}` since the error object isn't referenced.

Follow-up to 5f290345.

packages/cli/src/capture/contentExtractor.ts

@@ -280,7 +280,7 @@ export async function captionImagesWithGemini(
                 .png()
                 .toBuffer();
               pngBase64 = pngBuffer.toString("base64");
-            } catch (err) {
+            } catch {
               // SVG rasterization can fail on exotic features (external fonts,
               // foreignObject, filters with missing primitives). Skip caption
               // rather than block — agent will fall back to contact-sheet view.