fix: scope editor files and tabs per worktree

[AmethystLiang]

Problem

Editor files and tab state were shared globally across all worktrees. When switching between worktrees, files from other worktrees would appear in the tab bar, tab counts were incorrect, and the active file/tab type was not restored per-worktree. Closing a worktree also didn't clean up its associated editor files.

Solution

• Filter editor files by active worktree in the Terminal component so only relevant files appear in the tab bar and tab count
• Add per-worktree tracking of active file and tab type (activeFileIdByWorktree, activeTabTypeByWorktree) in the editor store
• Restore per-worktree editor state when switching worktrees via setActiveWorktree, with fallback to another open file if the remembered file was closed
• Clean up editor files and per-worktree state when a worktree is removed
• Scope closeFile and closeAllFiles to the active worktree
• Use type instead of interface for OpenFile and EditorSlice (lint fix)

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