Function sync_shared_agent_data

desktop/src-tauri/src/migration.rs:473–701

Create symlinks for shared agent data files from the current (worktree) data directory to the canonical dev data directory. Guards: - `BUZZ_SHARE_IDENTITY` must be `"1"` - `BUZZ_PRIVATE_KEY` must parse as valid `nostr::Keys` - The canonical dir must differ from the current dir (skip if we ARE canonical) - The canonical dir must exist

(app: &tauri::AppHandle)

/// - The canonical dir must differ from the current dir (skip if we ARE canonical)
/// - The canonical dir must exist
pub fn sync_shared_agent_data(app: &tauri::AppHandle) {
    // Guard: only runs when sharing identity with a worktree.
    let is_shared = std::env::var("BUZZ_SHARE_IDENTITY")
        .map(|v| v == "1")
        .unwrap_or(false);
    if !is_shared {
        return;
    }

    // Guard: BUZZ_PRIVATE_KEY must be a valid nostr key.
    let has_valid_key = std::env::var("BUZZ_PRIVATE_KEY")
        .ok()
        .and_then(|k| k.parse::<nostr::Keys>().ok())
        .is_some();
    if !has_valid_key {
        eprintln!("buzz-desktop: shared-agent-sync: BUZZ_PRIVATE_KEY missing or invalid, skipping");
        return;
    }

    let current_dir = match app.path().app_data_dir() {
        Ok(dir) => dir,
        Err(e) => {
            eprintln!("buzz-desktop: shared-agent-sync: cannot resolve app data dir: {e}");
            return;
        }
    };

    let canonical_dir = match canonical_dev_data_dir(&current_dir) {
        Some(dir) => dir,
        None => {
            eprintln!("buzz-desktop: shared-agent-sync: cannot compute canonical dir (no parent)");
            return;
        }
    };

    // Guard: skip if we ARE the canonical instance.
    // Use canonicalize to handle case-insensitive FS and symlinks.
    let current_canonical =
        std::fs::canonicalize(&current_dir).unwrap_or_else(|_| current_dir.clone());
    let source_canonical =
        std::fs::canonicalize(&canonical_dir).unwrap_or_else(|_| canonical_dir.clone());
    if current_canonical == source_canonical {
        return;
    }

    // Guard: skip if canonical dir doesn't exist.
    if !canonical_dir.exists() {
        eprintln!(
            "buzz-desktop: shared-agent-sync: canonical dir does not exist: {}",
            canonical_dir.display()
        );
        return;
    }

    // Seed-up: if canonical is missing a shared file but a sibling instance
    // holds real (non-symlink) content, migrate it up to canonical before the
    // symlink loop runs. Mirrors the SHARED_AGENT_DIRS migration below, applied
    // to individual files. Without this, a fresh write in a worktree is never