test: testing overhaul -- CI e2e gates, parallel suites, generated matrices, mutation testing (#215)

Closes the "e2e never runs in CI" hole. Adds per-PR e2e smoke gate,
nightly full-suite workflows, parallel vitest forks (per-fork DBs),
Playwright parallel/serial/visual projects against production builds,
metadata-generated test suites (drift guards, hostile inputs, format
matrix, pairwise settings, property-based fuzz), Stryker mutation
testing, Schemathesis API fuzz, coverage ratchet, and fixes for three
session-poisoning bugs that caused 200+ serial-bucket failures.

Bug fix included: favicon/split/bulk-rename could hang clients forever
when ZIP streaming failed after reply.hijack().

apps/api/src/routes/tools/bulk-rename.ts

@@ -103,6 +103,9 @@ export function registerBulkRename(app: FastifyInstance) {
           details: err instanceof Error ? err.message : "Unknown error",
         });
       }
+      // The ZIP stream already started; end the connection so clients see a
+      // truncated transfer instead of hanging forever.
+      reply.raw.destroy(err instanceof Error ? err : new Error(String(err)));
     }
   });
 }

apps/api/src/routes/tools/favicon.ts

@@ -106,6 +106,13 @@ export function registerFavicon(app: FastifyInstance) {
           buf = await autoOrient(buf);
         }
 
+        // Force a full pixel decode now. Header validation alone lets
+        // truncated files through, and a decode failure after reply.hijack()
+        // cannot be turned into an error response anymore.
+        if (validation.format !== "svg") {
+          await sharp(buf).stats();
+        }
+
         decodedFiles.push({ buffer: buf, filename: file.filename });
       } catch (err) {
         const reason = err instanceof Error ? err.message : "Unknown decode error";
@@ -206,6 +213,9 @@ export function registerFavicon(app: FastifyInstance) {
           details: err instanceof Error ? err.message : "Unknown error",
         });
       }
+      // The ZIP stream already started; end the connection so clients see a
+      // truncated transfer instead of hanging forever.
+      reply.raw.destroy(err instanceof Error ? err : new Error(String(err)));
     }
   });
 }

apps/api/src/routes/tools/split.ts

@@ -139,6 +139,13 @@ export function registerSplit(app: FastifyInstance) {
       const fullW = metadata.width ?? 0;
       const fullH = metadata.height ?? 0;
 
+      // Force a full pixel decode before streaming starts. Metadata alone
+      // lets truncated files through, and a decode failure after
+      // reply.hijack() cannot become an error response anymore.
+      if (validation.format !== "svg") {
+        await sharp(fileBuffer).stats();
+      }
+
       let cols = settings.columns;
       let rows = settings.rows;
       if (settings.tileWidth && settings.tileHeight) {
@@ -221,6 +228,9 @@ export function registerSplit(app: FastifyInstance) {
           details: err instanceof Error ? err.message : "Unknown error",
         });
       }
+      // The ZIP stream already started; end the connection so clients see a
+      // truncated transfer instead of hanging forever.
+      reply.raw.destroy(err instanceof Error ? err : new Error(String(err)));
     }
   });