fix: only emit components that are needed for css modules at the time of emission

[mohamedmansour]

The previous PR (#212) moved <style type="module"> emission from inline (inside each component's light DOM) to a blanket emission in for all inventoried components, and used document.querySelectorAll + manual CSSStyleSheet construction for SPA adoption. This had two problems:

1. Bloated SSR HTML with style definitions for every route-reachable component, including those not rendered on the current page.
2. document.querySelectorAll cannot pierce shadow DOM boundaries, so inline <style type="module"> tags were invisible to the framework.

What this changes

SSR: restore inline CSS module emission (handler)

emit_css_module() places the <style type="module" specifier="X"> tag inside the component's light DOM on first render:

  <my-comp><style type="module" specifier="my-comp">CSS</style><template ...>

The browser registers the CSS module globally from this tag and automatically adopts it via shadowrootadoptedstylesheets on the declarative shadow root. No JS needed during SSR hydration.

SSR: emit templates and inventory for rendered components only

Previously, body_end expanded rendered_components into a "reachable" set that included components inside unrendered / blocks. This caused inventory to cover components whose <style type="module"> definitions were never emitted (because emit_css_module only fires for actually-rendered components), creating a mismatch.

Now body_end emits template IIFEs and builds the inventory from rendered_components only. Components inside unrendered conditional blocks are excluded — they arrive via templateStyles[] + templates[] during SPA partial navigation. This ensures: if a component is in the inventory, both its template IIFE and its CSS module definition are in the document.

SPA: use import() with { type: "css" } for style adoption (framework)

For SPA-created components (no declarative shadow root), the framework uses the browser's CSS module registry directly:

  import(specifier, { with: { type: "css" } })

This returns the browser-registered CSSStyleSheet — no DOM queries, no manual CSSStyleSheet construction, no application-level cache. The browser's module registry is the cache (O(1) hash map lookup).

SSR-hydrated components skip this entirely — the browser already adopted the sheet from shadowrootadoptedstylesheets.