feat: enhance VS Code extension with sidebar redesign, improved API i… #8

Job	Run time
Frontend lint, typecheck & unit tests	22s
Rust check & test	1m 26s
Tauri build smoke test	3m 29s
1.x → 2.0 migration rehearsal	1m 4s
Offline critical journey tests	1m 38s
	7m 59s

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