fix: ignore temp files in Vite watcher to prevent dev server crash (#3763)

## Summary
- Adds default `server.watch.ignored` patterns to the Fresh Vite plugin
config
- Ignores `*.tmp.*`, `*.timestamp-*`, editor swap files (`*.swp`,
`*.swo`, `*~`, `.#*`)
- Prevents a `watchFs` race condition on Linux where Deno tries to open
a short-lived file that was already deleted, crashing the dev server
with `NotFound: No such file or directory`

Users can still override or extend these patterns in their own
`vite.config.ts` since Vite merges config from plugins.

Closes #3585

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartlomieju

packages/plugin-vite/src/mod.ts

@@ -91,6 +91,23 @@ export function fresh(config?: FreshViteConfig): Plugin[] {
         isDev = env.command === "serve";
 
         return {
+          server: {
+            watch: {
+              // Ignore temp files, editor swap files, and Vite timestamp
+              // files. On Linux, these short-lived files can trigger a
+              // watchFs race condition in Deno where the watcher tries to
+              // open a file that has already been deleted, crashing the
+              // dev server with ENOENT.
+              ignored: [
+                "**/*.tmp.*",
+                "**/*.timestamp-*",
+                "**/*~",
+                "**/.#*",
+                "**/*.swp",
+                "**/*.swo",
+              ],
+            },
+          },
           esbuild: {
             jsx: "automatic",
             jsxImportSource: "preact",

packages/plugin-vite/tests/config_test.ts

@@ -0,0 +1,26 @@
+import { expect } from "@std/expect";
+import { fresh } from "../src/mod.ts";
+import type { Plugin } from "vite";
+
+Deno.test("fresh plugin - sets server.watch.ignored patterns", () => {
+  const plugins = fresh() as Plugin[];
+  const freshPlugin = plugins.find((p) => p.name === "fresh");
+  expect(freshPlugin).toBeDefined();
+
+  // Call the config hook as Vite would during dev
+  // deno-lint-ignore no-explicit-any
+  const configFn = freshPlugin!.config as any;
+  const result = configFn({}, { command: "serve" });
+
+  const ignored = result?.server?.watch?.ignored;
+  expect(ignored).toBeDefined();
+  expect(Array.isArray(ignored)).toBe(true);
+
+  // Should ignore temp files, editor swap files, and Vite timestamp files
+  expect(ignored).toContain("**/*.tmp.*");
+  expect(ignored).toContain("**/*.timestamp-*");
+  expect(ignored).toContain("**/*.swp");
+  expect(ignored).toContain("**/*.swo");
+  expect(ignored).toContain("**/*~");
+  expect(ignored).toContain("**/.#*");
+});