[FEATURE] VS Code: make Focus view a per-tab/per-conversation setting instead of global

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

In the VS Code extension, Focus view (focusView, Ctrl+Alt+F, "Claude Code: Toggle Focus view") is global. The docs say the change "applies to every open session and persists across sessions".

I usually have several conversations open in separate tabs. A long-running autonomous one (infrastructure work, many gcloud/gh/git calls) is best read as prompts, replies and one-line tool rows. Another tab where I'm reviewing a diff or debugging a failing command needs the full tool input and output visible. Today I have to flip the global toggle every time I switch tabs, and doing so changes every other open conversation too.

Proposed Solution

Make Focus view settable per conversation tab, with the existing focusView setting as the default for new tabs:

• Toggle Focus view (and Ctrl+Alt+F) acts on the active Claude tab only.
• A small indicator or toggle in the tab/panel header shows the current state.
• The focusView setting keeps its meaning as the default applied to newly opened conversations.
• Optionally, a second command such as "Toggle Focus view for all sessions" keeps today's behaviour for anyone who wants it.

Alternative Solutions

• Toggle the global setting on every tab switch. This is slow and affects the other tabs.
• Set focusView in .vscode/settings.json per workspace. This separates projects but not tabs in the same workspace.
• Expand individual tool rows by hand. This works for one call but not for a whole stretch of a conversation.

Priority

Low - Nice to have

Feature Category

Configuration and settings

Use Case Example

1. Tab A runs a multi-step ticket-to-merge workflow with dozens of shell calls. I want Focus view on so I only read the narrative.
2. Tab B is where I'm checking why one specific command failed. I want the full tool output visible.
3. With a per-tab toggle I leave A in Focus view and turn it off in B, then switch between them without touching either.

Additional Context

Related but distinct: #98026 (Focus view should apply to the whole transcript), #83746 (keep human-related messages visible in Focus view), #99328 (Claude isn't told when Focus view is toggled mid-session). None of these ask for per-tab scope.

Docs reference: https://code.claude.com/docs/en/vs-code (Focus view and the focusView setting).