fix(compress-pdf): land close to the target size, honestly (#522)

Target-size compression had only a coarse DPI lever, so it undershot badly (a 350KB target could land at 216KB) and silently missed unreachable targets. Adds JPEG quality as a second lever (forced re-encode so it bites on JPEG scans), folds both into one monotonic quality axis that target-size binary-searches, reports targetMet honestly in the panel across 21 locales, and flips the tool to async for the extra passes. Quality-mode output sizes shift intentionally (slider now drives JPEG quality at full resolution in its top half).

packages/shared/src/constants.ts

@@ -1360,7 +1360,9 @@ const BASE_TOOLS: Tool[] = [
     route: "/compress-pdf",
     modality: "document",
     acceptedInputs: [".pdf"],
-    executionHint: "fast",
+    // "long": the target-size mode runs several ghostscript passes; async keeps
+    // the request off the sync window and surfaces a real progress bar.
+    executionHint: "long",
   },
   {
     id: "rotate-pdf",