Inline extensions: the frame never shrinks below its start height because the shell measures a body with min-height 100%

# Inline extensions: the frame never shrinks below its start height because the shell measures a body with `min-height: 100%`

**Version:** `@agent-native/core` 0.176.4.

**What happens.** A transient `render-inline-extension` control with one row of buttons renders inside a frame 260 pixels tall (the `initialHeight` default). The frame grows when content is taller but never shrinks to fit shorter content.

**Why.** `dist/extensions/html-shell.js` reports `Math.max(document.documentElement.scrollHeight, document.body.scrollHeight)` on resize, and the shell's own stylesheet (`dist/client/extensions/portable-extension.js`) sets `html, body { min-height: 100% }`. The document is therefore always at least as tall as the iframe viewport, so the reported height is never smaller than the current height, and `InlineExtensionFrame` (which honours reports down to 96 pixels) never receives a smaller value.

**Expected.** Measure the content, not the viewport: drop `min-height: 100%` from the shell body, or report the height of a content wrapper element, so a one-row control renders at its natural height plus padding.

**Workaround used.** Every control passes `initialHeight: 120` (the schema floor) so the frame starts small and only grows.

Inspect dist/extensions/html-shell.js and dist/client/extensions/portable-extension.js, then trace how InlineExtensionFrame handles reported heights down to 96 pixels. Verify the shell measures content rather than the iframe viewport, and confirm that a one-row inline control shrinks to its natural height plus padding while taller content still grows.

Written by the indexing model from the issue text.