fix: correct fullscreen lifecycle on comparison maps

[vbhjckfd]

Summary

• Collapsing a similar-route entry while its comparison map was fullscreen stranded the browser in fullscreen on a torn-down element (cmpDrop called map.remove() with no check for document.fullscreenElement).
• Reopening/closing the same entry repeatedly stacked one fullscreenchange listener per rebuild on the same div, each closing over an already-remove()-d map instance.

Fix

• cmpDrop: exit fullscreen before removing the map if the map's container is currently fullscreen.
• addFullscreenControl: bind the listener once per div (_fsBound guard), and resolve the live map through the _cmpMaps registry by key at fire time instead of a closed-over m.

Route-detail maps (last column) are unaffected — they're built once and never rebuilt, so neither bug applies there.

Based on #117 (comparison-map feature) — targets that branch, not master.

Test plan

• npx vitest run tests/actions/getAllRoutesAction.test.js (6 passed)
• npx vitest run full suite (212 passed)
• Verified emitted trailing <script> still parses standalone
• Manual: expand entry, go fullscreen, collapse <details> without exiting fullscreen first — page should return to normal
• Manual: open/close/reopen same entry a few times, confirm only one fullscreenchange listener is attached (devtools getEventListeners)