fix(record): recover failed Trace exports and hint --url when the default start page fails

Reject legacy JSON --output before recording starts, persist the completed Trace before writing the bundle so `bsk record stop --output <dir>` can retry after an export failure, and tell users to pass --url when https://example.com/ does not load.

crates/bsk-cli/src/cli/record_recovery.rs

@@ -0,0 +1,113 @@
+//! Persist a completed Trace so a failed bundle export can be retried.
+
+use std::fs;
+
+use anyhow::{Context, Result};
+use bsk_protocol::tools::RecordedTrace;
+
+use crate::daemon::paths;
+
+pub fn save(trace: &RecordedTrace) -> Result<()> {
+    let path = paths::record_recovery_path()?;
+    paths::ensure_bsk_home()?;
+    let json = serde_json::to_string_pretty(trace).context("serialize record recovery")?;
+    let tmp = path.with_extension("tmp");
+    fs::write(&tmp, format!("{json}\n")).with_context(|| format!("write {}", tmp.display()))?;
+    fs::rename(&tmp, &path).with_context(|| format!("commit {}", path.display()))?;
+    Ok(())
+}
+
+pub fn load() -> Result<Option<RecordedTrace>> {
+    let path = paths::record_recovery_path()?;
+    if !path.exists() {
+        return Ok(None);
+    }
+    let raw = fs::read_to_string(&path).with_context(|| format!("read {}", path.display()))?;
+    let trace = serde_json::from_str(&raw).with_context(|| format!("parse {}", path.display()))?;
+    Ok(Some(trace))
+}
+
+pub fn exists() -> bool {
+    paths::record_recovery_path()
+        .map(|path| path.exists())
+        .unwrap_or(false)
+}
+
+pub fn clear() {
+    if let Ok(path) = paths::record_recovery_path() {
+        let _ = fs::remove_file(path);
+    }
+}
+
+#[cfg(test)]
+pub(crate) fn test_env_lock() -> std::sync::MutexGuard<'static, ()> {
+    static GUARD: std::sync::Mutex<()> = std::sync::Mutex::new(());
+    GUARD.lock().unwrap_or_else(|e| e.into_inner())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use bsk_protocol::tools::{
+        RecorderInfo, StopReason, TRACE_VERSION_V3, TraceEntry, TraceStateV3, TraceV3,
+        VOM_FORMAT_VERSION,
+    };
+
+    fn sample_trace() -> RecordedTrace {
+        RecordedTrace::V3(TraceV3 {
+            version: TRACE_VERSION_V3,
+            recorded_at: "2026-08-10T02:12:55.360Z".into(),
+            stopped_by: StopReason::UserFinish,
+            entry: TraceEntry {
+                start_url: "https://example.com/".into(),
+            },
+            recorder: RecorderInfo {
+                bsk: "0.1.10".into(),
+                vom: VOM_FORMAT_VERSION,
+            },
+            states: vec![TraceStateV3 {
+                id: "s1".into(),
+                url: "https://example.com/".into(),
+                title: Some("Example".into()),
+                body: "@vom 1\nL1 page".into(),
+                truncated: false,
+            }],
+            steps: vec![],
+            purpose: None,
+            started_at: None,
+        })
+    }
+
+    fn with_temp_home<F: FnOnce()>(f: F) {
+        let _lock = test_env_lock();
+        let tmp = tempfile::tempdir().unwrap();
+        unsafe {
+            std::env::set_var(crate::daemon::paths::BSK_HOME_ENV, tmp.path());
+        }
+        f();
+        clear();
+        unsafe {
+            std::env::remove_var(crate::daemon::paths::BSK_HOME_ENV);
+        }
+    }
+
+    #[test]
+    fn save_load_round_trips() {
+        with_temp_home(|| {
+            let trace = sample_trace();
+            save(&trace).unwrap();
+            assert!(exists());
+            assert_eq!(load().unwrap(), Some(trace));
+        });
+    }
+
+    #[test]
+    fn clear_removes_recovery_file() {
+        with_temp_home(|| {
+            save(&sample_trace()).unwrap();
+            clear();
+            assert!(!exists());
+            assert_eq!(load().unwrap(), None);
+        });
+    }
+}