cmux-debugging

# cmux Debugging ## Debug event log Put debug event instrumentation (keys, mouse, focus, splits, tabs) in the unified DEBUG build log. This is not a requirement to log every new code path; most probes belong to a dogfood debug loop and are removed before merge. ```bash tail -f "$(cat /tmp/cmux-last-debug-log-path 2>/dev/null || echo /tmp/cmux-debug.log)" ``` - Untagged Debug app logs to `/tmp/cmux-debug.log`; tagged (`./scripts/reload.sh --tag <tag>`) to `/tmp/cmux-debug-<tag>.log`. - `reload.sh` writes the current log path to `/tmp/cmux-last-debug-log-path` and the selected dev CLI path to `/tmp/cmux-last-cli-path`, and points `/tmp/cmux-cli` and `$HOME/.local/bin/cmux-dev` at that CLI. - Implementation: `Packages/macOS/CMUXDebugLog/Sources/CMUXDebugLog/DebugEventLog.swift`. App shim: `Sources/App/DebugLogging.swift`. Both are `#if DEBUG`, so every call site must be wrapped in `#if DEBUG` / `#endif`. - `cmuxDebugLog("message")` timestamps and appends in real time. A 500-entry ring buffer backs it; `CMUXDebugLog.DebugEventLog.shared.dump()` writes the full buffer to file. - Key events are logged in `AppDelegate.swift` (monitor, `performKeyEquivalent`); mouse/UI events inline in views (`ContentView`, `BrowserPanelView`). - Stable event prefixes: `focus.panel`, `focus.bonsplit`, `focus.firstResponder`, `focus.moveFocus`, `tab.select`, `tab.close`, `tab.dragStart`, `tab.drop`, `pane.focus`, `pane.drop`, `divider.dragStart`. ## Debug menu DEBUG builds get a **Debug** menu i...