fix: pg:copy confirmation prompt shows addon name not app name

[heroku-johnny]

Summary

• Bug: pg:copy destructive-action confirmation prompt asked users to type the app name to confirm, even when the target was a named Heroku PostgreSQL attachment. A user copying to the wrong database on the same app would see an identical prompt for both, providing no safety signal.
• Data-loss risk: Because the confirm value was always the app name, not the specific database, a mistaken heroku pg:copy SOURCE TARGET against the wrong database on the same app would clear and overwrite data with no distinguishing warning. This is a real data-safety gap.
• Fix: Extract the human-readable addon name (e.g. JADE, CRIMSON) from the config-var attachment name and use it for both name and confirm, mirroring the existing behavior of the postgres:// URL branch which already correctly uses conn.database || conn.host.

Fixes: W-23597886
Related: #1545

Before / After

Before — both prompts for two databases on the same app look identical:

WARNING: Destructive action
This command will remove all data from JADE
Type my-app to confirm: _

After — each prompt names the specific database:

WARNING: Destructive action
This command will remove all data from JADE
Type JADE to confirm: _

Test plan

• heroku pg:copy SOURCE TARGET --app my-app where target is a named attachment: prompt asks you to type the addon name (e.g. JADE), not the app name.
• heroku pg:copy postgres://... TARGET --app my-app: existing behavior unchanged — prompt still uses conn.database || conn.host.
• Providing the wrong confirmation string still aborts without copying.
• --confirm JADE flag bypasses the prompt correctly.

🤖 Generated with Claude Code

[tlowrimore-heroku]

LGTM

[tlowrimore-heroku]

Actually, it looks like something has broken the integration tests.

[tlowrimore-heroku]

LGTM!