chore: remove unnecessary <template shadowrootmode="open"> wrappers

[mohamedmansour]

The <template shadowrootmode="open"> wrapper is optional in component HTML source files — the WebUI build tool auto-injects it when absent. The wrapper is only needed when the author wants to attach host-level events or extra attributes to the template tag, e.g.:

<template shadowrootmode="open"
  @toggle-item="{onToggleItem(e)}"
  @delete-item="{onDeleteItem(e)}"
>

All other usages are redundant boilerplate that bloats templates.

HTML templates (55 files):

Remove the plain <template shadowrootmode="open"> opening tag and </template> closing tag, then dedent content by 2 spaces. Covers:

• examples/app/commerce/ — 17 component templates
• examples/app/routes/ — 1 component template
• packages/webui-framework/tests/fixtures/ — 37 test fixture templates

Files with host-level events are preserved unchanged:

• todo-fast/todo-app, todo-fast/todo-item (@toggle-item, @delete-item, @click)
• todo-webui/todo-app, todo-webui/todo-item (@toggle-item, @delete-item, @click)
• calculator/calc-app, calculator/calc-button (@button-press, @click)
• commerce/mp-app (@toggle-cart, @toggle-mobile-menu)
• contact-book-manager/cb-app (@search-change, @select-contact)
• fixtures/list/test-list (@toggle-item)
• fixtures/root-event/test-root-event (@click)

Documentation (8 files):

Remove the wrapper from source-template code examples in:

• DESIGN.md — outlet example
• docs/tutorials/todo-app.md — todo-item template
• docs/guide/concepts/routing.md — 4 shell/page examples
• docs/guide/concepts/hydration.md — 2 source template examples
• docs/guide/concepts/directives/route.md — 2 outlet examples
• docs/guide/ai.md — outlet example
• packages/webui-router/README.md — shell example
• packages/webui-framework/tests/fixtures/README.md — template guide
• .github/skills/testing/SKILL.md — fixture scaffold example

SSR output examples (showing what the build produces) and conceptual references explaining the shadowrootmode attribute are preserved.