Set Campaign Business Name

Fixes the BUSINESS NAME shown in a campaign's ads — the one place a typo is visible to every person who sees the ad, and until now there was no way to correct it.

Text assets in Google Ads are IMMUTABLE: `asset.text_asset.text` cannot be edited, which is why no update tool could exist. The change is a RELINK, done in one atomic request: it finds an asset in the account that already carries the exact text (so a name already used elsewhere is REUSED instead of duplicated), creates one only if none exists, links it to the campaign as BUSINESS_NAME and unlinks the old one in the same mutate; a campaign accepts only one business name, so the swap happens together.

With `text` empty it READS what the campaign shows today without changing anything. confirm=false returns a dry run naming the old and the new text; confirm=true applies it and reads the value back from Google. Fixing a name used by several campaigns means calling this once per campaign, because the link is per campaign.