WebMCP: Implement tool name validation

The spec PR webmachinelearning/webmcp#152 is
tightening tool name validation to match what the MCP specification
accepts [1], and we think it's reasonable for the web platform to throw
exceptions when tool names do not match this criteria, which is what
this CL does.

[1]:
https://modelcontextprotocol.io/specification/2025-11-25/server/tools#tool-names

R=masonf

Bug: 489045948
Change-Id: I7d1af5d8cd18e5be7db5ddc9f9ce6d28e73cfd3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7744064
Commit-Queue: Dominic Farolino <dom@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1625865}

Author: domfarolino

webmcp/imperative/register_tool_name_validation.https.window.js

@@ -0,0 +1,71 @@
+test(() => {
+  // Valid names
+  const validNames = [
+    'a',
+    'A',
+    '0',
+    'valid-name',
+    'valid_name',
+    'valid.name',
+    'valid-name.with_extras-123',
+    'a'.repeat(128)
+  ];
+
+  for (const name of validNames) {
+    navigator.modelContext.registerTool({
+      name: name,
+      description: 'valid name test',
+      execute: async () => 'empty'
+    });
+  }
+}, 'Valid tool names are accepted.');
+
+test(() => {
+  // Invalid names
+  const invalidNames = [
+    '', // Empty
+    'a'.repeat(129), // Too long
+    'name with space',
+    'name@special',
+    'name#special',
+    'name$special',
+    'name%',
+    'name^',
+    'name&',
+    'name*',
+    'name(',
+    'name)',
+    'name+',
+    'name=',
+    'name[',
+    'name]',
+    'name{',
+    'name}',
+    'name|',
+    'name\\',
+    'name:',
+    'name;',
+    'name"',
+    'name\'',
+    'name<',
+    'name>',
+    'name?',
+    'name/',
+    'name`',
+    'name~',
+  ];
+
+  for (const name of invalidNames) {
+    assert_throws_dom(
+      'InvalidStateError',
+      () => {
+        navigator.modelContext.registerTool({
+          name: name,
+          description: 'invalid name test',
+          execute: async () => 'empty'
+        });
+      },
+      `Tool name '${name}' is invalid.`
+    );
+  }
+}, 'Invalid tool names throw InvalidStateError.');