ingestd/vectord: remove two fragile unwraps on Option paths

Both were technically safe — guarded above by map_or(true, ...) and
Some(entry) assignment respectively — but relied on multi-line
invariants that a future refactor could easily break.

  - ingestd/watcher.rs:80: path.file_name().unwrap() on a path that
    was already checked via map_or(true, ...) two lines up. Fix:
    let-else binds filename once, no double lookup, no unwrap.

  - vectord/promotion.rs:145: file.current.as_ref().unwrap() called
    TWICE on the same line to log config + trial_id. Guard via
    `if let Some(cur) = &file.current` so the log gracefully skips
    if the invariant ever breaks instead of panicking at runtime.

Both are drop-in semantically: happy path identical, error path now
graceful-skip instead of panic. Workspace warnings still at 0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/ingestd/src/watcher.rs

@@ -72,12 +72,14 @@ async fn process_inbox(
 
         let path = entry.path();
 
-        // Skip directories and hidden files
-        if path.is_dir() || path.file_name().map_or(true, |n| n.to_string_lossy().starts_with('.')) {
-            continue;
-        }
-
-        let filename = path.file_name().unwrap().to_string_lossy().to_string();
+        // Skip directories and hidden files. Bind filename once via
+        // let-else so the subsequent use is unwrap-free — previous
+        // version relied on a map_or guard above + an .unwrap() here
+        // being consistent, which is a fragile invariant.
+        if path.is_dir() { continue; }
+        let Some(fn_os) = path.file_name() else { continue; };
+        let filename = fn_os.to_string_lossy().to_string();
+        if filename.starts_with('.') { continue; }
         tracing::info!("watcher: found new file '{}'", filename);
 
         // Read file