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feat: prove T313, hyperconnected implies the countable chain condition - #1335

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feat: prove T313, hyperconnected implies the countable chain condition#1335
kisonecat wants to merge 1 commit into
felixpernegger:masterfrom
kisonecat:formalize-T313

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Adds T313: a hyperconnected space satisfies the countable chain condition.

A hyperconnected space has no two disjoint nonempty open sets at all, so a pairwise disjoint
family of open sets has at most one nonempty member. Such a family is contained in
insert ∅ {one set}, hence countable — the bound is far stronger than countability.

Closes #567.

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T313: Hyperconnected (P39) => Countable chain condition (P29)

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