Try direct BLE authentication before double-connect fallback

[alexanderpett]

Draft PR inside the fork for review/testing before opening upstream.

Summary:

• Try authentication on the initial BLE connection first.
• Attach the disconnect callback to the initial client.
• Only use the existing 5-second disconnect/reconnect workaround as a fallback if the first authentication fails.

Why:

• The unconditional double-connect workaround appears to break some setups by forcing a reconnect on every mesh connection attempt.
• A fully removed workaround fixed my Home Assistant / Plejd setup, but issue pyplejd 0.21.1: double-connect firmware workaround causes BLE reconnect throttling and progressively shorter connections thomasloven/hass-plejd#154 indicates the workaround may still be needed for some hardware/firmware combinations.
• This branch is therefore more conservative than ha-no-double-connect and is the better candidate for an upstream PR.

Related:

• Plejd: Commands to non‑gateway devices only take effect after integration reload (HA 2026.6 + hass‑plejd 0.21.3) thomasloven/hass-plejd#162
• pyplejd 0.21.1: double-connect firmware workaround causes BLE reconnect throttling and progressively shorter connections thomasloven/hass-plejd#154

Local tested workaround:

• ha-no-double-connect branch, installed via hass-plejd fork, confirmed working with pyplejd 0.21.3.post1.

This branch has only one file changed and no version bump.