feat(connections): give each database in the connections strip its own tabs

[datlechin]

Why

With many databases or tenant schemas on one connection, every database's tabs piled into one tab strip, and same-named tables were easy to mix up. The connections strip already lists each database as an entry, but only a connection switch swapped the tabs. A database switch from the toolbar or sidebar left the previous database's tab on screen.

Change

• Each connections-strip entry owns its tabs. The tab strip shows the entry you are on; the others keep theirs. No setting.
• Every database switch, MCP switch_database and switch_schema included, lands on that database's last tab. Picking a tab of another database moves the sidebar there without changing the saved default.
• Query tabs stay on the database or schema they were opened in. The editor's picker also rebinds schemas on Oracle-style engines.
• Same-name fixes: Quick Switcher Open badge, inspector Table Info, and links, AppleScript and MCP open_table_tab matching. Dropped databases leave the strip.

Verified

QueryTabManagerVisibleContainerTests and VisibleContainerFollowingTests are new. Changed on purpose: SwitchDatabaseTests, WorkspaceAnchoringTests, WorkspaceRailStoreTests and CommandActionsBulkCloseTests (empty tabs now list their entry), QueryTabManagerRecencyTests (deferral removed). Checked against MariaDB with two tenants.

Screenshots

Before	After

Not in this PR

• A hidden entry shows no finished-query mark in the strip, as a background connection does not today.
• PostgreSQL schemas inside one database stay one entry.

Fixes #3431