fix(tui): keep saved tabs separate by server

[abeisleem]

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.

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?

• 49 focused tests and the TUI typecheck passed after updating to upstream v2.
• The push hook passed all 35 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

pr-47999.mov

Checklist

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

[github-actions]

Thanks for your contribution!

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Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

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