fix(tui): keep saved tabs separate by server - #47999

Issue for this PR

Closes #47998

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Keeps saved TUI tabs and terminal selections separate for each server, so opening a remote TUI cannot reuse or overwrite the local layout. Both global and current-directory tab scopes are isolated, including when servers have identical session and terminal IDs.

The managed local server keeps its legacy storage and a stable identity across endpoint changes. Explicit server URLs use a normalized, credential-free identity; terminal lists use that identity too.

Legacy layouts are preserved for managed local use. If an older client already saved remote tabs into that layout, those stale entries may need closing manually; this fix prevents future mixing but does not reconstruct historical ownership.

A saved-server picker could build on this later (#37667). Opening remote sessions as tabs remains a separate request (#45346). #18302 is an analogous desktop-app issue.

How did you verify your code works?

• 70 focused tests and the TUI typecheck passed after updating to upstream v2.
• The push hook passed all 36 repository typecheck tasks.
• Manually checked and recorded local/remote behavior before and after the fix.
• An earlier full-suite run had three unrelated plugin-source failures.
• To verify manually, open tabs locally, launch with --server <url> using the same storage channel and launch directory, change the remote tabs, then return locally. Each server should restore only its own layout.

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR