feat: add doctor command for diagnosing installs and cleaning stale daemon state (#1254)

* feat: add `doctor` command for install diagnostics and cleanup

Adds `agent-browser doctor`, a one-shot diagnostic that checks
environment, Chrome install, daemon state, config, encryption key,
providers, network reachability, and a live headless launch test.
Auto-cleans stale `.sock` / `.pid` / `.version` / `.stream` sidecar
files on every run. Destructive repairs (reinstall Chrome, purge old
state, close version-mismatched daemons, generate missing encryption
key) are gated behind `--fix`. Supports `--offline`, `--quick`, and
`--json`.

* fixes

cli/src/flags.rs

@@ -771,6 +771,10 @@ pub fn clean_args(args: &[String]) -> Vec<String> {
         "--verbose",
         "-q",
         "--quiet",
+        // doctor-specific flags; harmless on other commands (ignored)
+        "--offline",
+        "--quick",
+        "--fix",
     ];
     // Global flags that always take a value (need to skip the next arg too)
     const GLOBAL_FLAGS_WITH_VALUE: &[&str] = &[