Option to disable auto-collapsing of tall code blocks

Since #11358 (v1.7.0) code blocks taller than roughly half the viewport are automatically collapsed when a document opens (shared/editor/nodes/CodeFence.ts — findTallBlocks with COLLAPSE_HEIGHT_RATIO). The collapse state is purely view-layer: it is recomputed on every load, is not persisted anywhere, and there is no setting to opt out. For teams that use Outline as a working store — pages of pasted tool output, logs, long config dumps — this is a recurring annoyance (also raised in #12336): • Reading a long page turns into a series of expand clicks that break linear reading • Outline's own find panel auto-expands matches since the fix for #12375, but the browser's native find can land on a match that stays visually hidden inside a collapsed block • The known workaround is to fork and remove collapsePlugins() entirely, which also removes the manual Collapse control and has to be reapplied on every merge Proposal: an opt-out that keeps the feature for thos…