feat(samples): add sample-size reporter for auto-fitting docs iframes

[desig9stein]

Related to: IgniteUI/igniteui-astro-components#108

Demos on the docs site render inside cross-origin iframes. By default
styles.scss pins html/body to height:100% + overflow:hidden, so an
iframe can only ever echo its own height back — it can't grow to fit its
content. This adds the demo-side half of a small postMessage handshake
with the docs host (astro-components' sample-widget) so samples that opt
into fitContent size themselves to their actual content.

How it works:

• the host posts { type: 'igd-sample-fit', width? } into the iframe on
  load; until that arrives the reporter stays completely dormant, so
  fixed-height demos and their percentage layouts are untouched
• on enable, it injects a one-time stylesheet that releases the viewport
  pin (height:auto, overflow:visible) and reports content size back with
  { type: 'igd-sample-height', height, width? } immediately and on every
  resize (via ResizeObserver)
• width is measured from the right-most element edge rather than the body
  box, mirroring the host's same-origin measurement, and is only computed
  when the host asks for it

Notes:

• no-ops outside an iframe (window.parent === window) and when there is
  no window (SSR/prerender)
• replies target the host's captured origin instead of broadcasting to
  '*', and only ever emit layout dimensions
• shared across all three Angular apps (src, app-crm, app-lob) via the
  "@shared/sample-size-reporter" tsconfig path alias so there is a single
  source of truth