docs(skills): state that no channel verb creates an integration

[ysyneu]

Why

reference/channel.md documents --plugin-ids as "IDs of plugins (integrations) subscribed to this channel" and says nothing about where those integrations come from. Read as a capability claim it implies the CLI can set one up, so a "how do I connect my mailbox / this alert source" question becomes an exhaustive search of the command tree — webhook --help, datasource --help, account --help, a full __dump-commands dump and several jq passes over it — which can only ever conclude that the verb is not there.

It is not there by design: creating or configuring an integration, and reading its inbound address/token, are console-side operations that the open API this CLI speaks does not expose. Absence is currently only discoverable by exhaustive search, which is the expensive way to learn a boundary.

What

One gotcha bullet on the channel card, placed next to the flag that implies the capability:

• --plugin-ids subscribes integrations that already exist; no verb creates or configures one.
• Integration creation and its inbound address/token are console-only, outside this CLI's API surface — so they are absent from the command tree by design.
• Answer "how do I connect X" from the product documentation and point at the console; don't grep the command tree for a verb that cannot exist.
• channel info reports the channel's own fields, not integration credentials.

Verification

• go build ./... clean
• go test ./internal/skilldoc/... passes
• Docs-only; no command surface or generated fence touched.