Discord: initialize DiscordAdapter in ready() instead of OnceLock on first message

[thepagent]

Parent: #382

Problem

discord::Handler stores adapter: OnceLock<Arc<dyn ChatAdapter>> and initializes it lazily on the first message() event via get_or_init(). This works but is slightly fragile — if ready() fires but no message ever arrives, the adapter is never created.

Suggested fix

Initialize the DiscordAdapter in the ready() handler where ctx.http is already available. This provides a cleaner lifecycle and guarantees the adapter exists as soon as the bot is connected.

Severity: nit — no functional impact, purely code hygiene.

[github-actions]

Thanks for the report! It looks like this issue was created without a template and is missing some required fields. Please add one of the following labels: bug, feature, documentation, or guidance, then edit this issue to include the matching template fields — the incomplete label will be removed automatically.

[thepagent]

Closing — no functional impact, purely code hygiene. The OnceLock pattern works correctly and the adapter is always initialized before use.