A second click while the first window was still being built removed its
registry entry, giving a broken window, a duplicate and a cap bypass. The
registry now records when a window is built; `reserve` dedupes, prunes only
built entries whose window is gone (any state, so a leak cannot hold a cap
slot), and enforces the cap in one critical section. Choosing a file already
open elsewhere focuses that window and closes the chooser instead of
resolving a second entry. The not-running sentence names the real action.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
shadowdaoandClaude Opus 5.5
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