v6: Make the font-size setting reach body text

[trevor-scheer]

Summary

• --font-size-body is declared twice: as a scaling preset token in tokens.css (:root, [data-font-size='default'|'compact'|'large'|'xl']), and as a frozen v5 value in root.css's DEPRECATED .graphiql-container block. Both selectors have specificity (0,1,0) and the frozen block comes later (after @import 'tokens.css'), so calc(15rem / 16) always won.
• Every consumer of var(--font-size-body) — the .graphiql-container base font-size, button, dialog, dropdown-menu, top-bar, and the collections / doc-explorer / query-builder plugins — has silently been pinned to 15px, so Settings > Font size never touched body text even though the code looked correct. The sibling preset tokens (--font-size-small, --font-size-mono, --font-size-eyebrow) were unaffected because they aren't redeclared in that block.
• Renaming the frozen declaration separates the two meanings and lets the preset token win.

Changes

• root.css: renamed --font-size-body: calc(15rem / 16) to --font-size-body-legacy in the DEPRECATED .graphiql-container block.
• graphiql-plugin-code-exporter/src/index.css: pointed the CodeMirror-based plugin at var(--font-size-body-legacy) so it keeps rendering at the frozen 15px.
• Updated the DEPRECATED block comment to name the code-exporter plugin — the explorer plugin it referenced no longer consumes this token.

Validation Steps

1. Open the app and note the size of body text (panel headers, buttons, top bar, doc explorer rows).
2. Open Settings > Font size and switch to Large, then Extra large. Body text throughout the app should visibly grow at each step — previously it stayed fixed at 15px regardless.
3. Switch to Compact. Body text should visibly shrink.
4. Switch back to Default and confirm body text settles at the standard size (slightly smaller than before this change).
5. Open the code exporter plugin and cycle through the font-size presets. Its exported-code panel should stay the same size at every preset — it intentionally remains frozen.

[changeset-bot]

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