Lift the liquid glass buttons off the ButtonSize axis

[StylianosGakis]

Extract the glass button outside of the entire rest of the button system because it does not respect the multiple-size scenario anyway and we had to do if-checks for the glass scenario to adjust the size of the button due to this fact. We had code like

@Composable
private fun ButtonSize.sizeIn(style: Style): Size = when {
  style.glassMaterial != null && this == ButtonSize.Large -> Size.Glass
  else -> size
}

which felt wrong so I figured might as well take that special case out since we only have one size in the app for now. If we get more such buttons we can consider bringing it back into the same size system

🤖 AI description:

📄 The button seam — visual walkthrough of the final API, the size scale, and the Figma mapping.

sizeIn(style) let a ButtonStyle reach across and change the metrics a ButtonSize asked for, gated on this == ButtonSize.Large. So RoundedPrimary at Medium silently rendered with standard Medium padding: no error, no warning. Nothing hit it today (all three call sites are Large), but design-showcase was rendering the bogus combinations.

• RoundedPrimary/RoundedLiquidGlass leave ButtonStyle for LiquidGlassButtonStyle { Tinted, Regular }.
• New HedvigLiquidGlassButton, which takes no ButtonSize.
• Both funnel into a private ButtonImpl receiving Style and Size already resolved, so the axes can't cross. sizeIn() is deleted.
• Showcase gets a dedicated Glass row instead of a cell per size.

The misuse is now a compile error, not a silent fallback. Three probes against the new API:

Argument type mismatch: actual type is 'ButtonDefaults.LiquidGlassButtonStyle',
  but 'ButtonDefaults.ButtonStyle' was expected.
No parameter with name 'buttonSize' found.
Unresolved reference 'RoundedPrimary'.

The two enums are disjoint, HedvigLiquidGlassButton has no size parameter, and Size is a private sealed interface so Size.LiquidGlass isn't nameable outside Button.kt. (Modifier.liquidGlass stays public for ToolbarIcons, so a glass material can still be hand-applied to any button — but that's explicit, and nothing gets silently substituted.)

Naming, following @panasetskaya's review comment. She was right that Primary isn't glass: it resolves to the same nine color tokens as ButtonStyle.Primary at every state. But the Figma file settles what these actually are. Make a claim and Help & support are two instances of one component with a boolean Tinted variant, and both BG children carry the same drop shadow, 0px 8px 40px rgba(0,0,0,0.12), which is exactly our glassDropShadow. So they are a pair, design calls the pair liquid glass, and the code now says the same.

Metrics check out against Figma: fill #121212, 20dp horizontal padding, 48dp height (12 + 24 + 12), full corner radius.

Verified on a Pixel 6 Pro: home action row renders all three buttons correctly, and the showcase shows the six remaining styles per size plus the Glass row.

[panasetskaya]

the only comment now it that this button now that we have all buttons rounded is just a Primary. It's not glass in itself.