feat: HMR support for inline template changes

[BenjaminDobler]

Problem

When a component uses an inline template (template: \...`), any change to the .tsfile triggers a full page reload — even if only the template string was modified. External.htmltemplates get proper HMR via the customfs.watchhandler, but inline templates don't benefit from this because the template is embedded in the.ts` file.

This means developers using inline templates (common in Angular 17+ standalone components) get a significantly worse DX than those using external templates.

Reproduction

1. Create a component with template: \

   Hello

   ``
2. Run dev server with liveReload: true
3. Change the template to template: \

   World

   ``
4. Observe: full page reload instead of HMR

Fix

In handleHotUpdate, before triggering a full reload for a component .ts file change, check if only the inline template portion changed:

1. Cache inline template content during transform — store the template string for each component file
2. On file change, diff old vs new — extract the new template, compare with cached version
3. If only the template changed — add to pendingHmrUpdates and send angular:component-update event (same mechanism as external templates)
4. If non-template code also changed — fall through to full reload (unchanged behavior)

The existing HMR middleware endpoint already handles inline templates via extractInlineTemplate(), so no middleware changes are needed — it just needs a pendingHmrUpdates entry to serve the update.

Test plan

• Inline template edit → verify HMR live update (no full reload)
• Non-template .ts edit (e.g., change a method) → verify full reload still triggers
• Mixed change (template + class code) → verify full reload
• External template edit → verify existing HMR still works (no regression)
• Component with no inline template → verify no change in behavior