feat: sleep/wake sessions, --clean flag, active-terminal highlight

[AThraen]

Summary

• Sleep/wake sessions — 💤 button on each session tears down the PTY but keeps the session in the sidebar (muted, at bottom). Click to wake, which re-runs the same restore path used at startup.
• `--clean` CLI flag — start with no preloaded sessions and skip all state writes for the run, so `state.json` is left untouched. Useful for debugging.
• Active-terminal accent ring — the active session's pane gets a 2px accent border so it's easy to spot in multi-pane layouts.
• `AutoResumeClaude` setting — toggle in Settings to disable the auto-injected `--resume ` on session restore.
• Layout persistence fix — `MainViewModel.Layout` was being saved/loaded but `_currentLayout` never synced after restore; now hooked via PropertyChanged.
• TerminalBridge accelerator-key fix — newer WebView2 WPF wrapper forwards accelerators through standard `PreviewKeyDown`; switched off the missing `CoreWebView2Controller.AcceleratorKeyPressed`.
• CLAUDE.md updated with all of the above.

Test plan

• Launch the app normally — saved sessions restore as before.
• Launch with `--clean` — no sessions appear, settings/sessions are not modified on close.
• Sleep an active session — sidebar shows muted dormant entry at bottom; pane disappears; remaining panes re-layout.
• Wake a dormant session — terminal relaunches; if it's a Claude session and `AutoResumeClaude` is on, prior conversation is picked up.
• Multi-pane layout — selected pane shows a 2px accent ring; switching active sessions moves the ring.
• Toggle `AutoResumeClaude` off, restart — Claude sessions launch without `--resume`.
• Switch layout (e.g. 2x2), close and reopen — layout is restored.
• Ctrl+T / Ctrl+W / Ctrl+F still work when terminal has focus (accelerator-key forwarding).

🤖 Generated with Claude Code