fix: preserve standalone BLE state during coordinator flaps

[svc-finitelabs]

Summary

• make coordinator bind and unbind transitions non-destructive
• preserve standalone BLE selections and dynamic bindings when the coordinator link flaps
• resume standalone bound devices after coordinator disconnects
• add an unreleased changelog entry

Testing

• lua -e 'assert(loadfile("src/esphome/capabilities/bluetooth_proxy.lua"))'

[svc-finitelabs]

Pushed a follow-up fix for the failing build check. The previous commit updated \ but left the generated changelog section in \ out of sync, so CI detected a dirty tree after . The branch now includes the generated README/changelog sync update in d0a3e29, and the workflow should go green on the next run.

[svc-finitelabs]

Correction to my last comment: the previous commit updated CHANGELOG.md but left the generated changelog section in README.md out of sync, so CI detected a dirty tree after make build. I pushed commit d0a3e29 to sync the generated docs, and the workflow should pass on the next run.