feat(api): brain_promote and brain_reject act on notes parked in raw/needs-review/ (#208)

brain_pending lists a parked note under its bare filename, but promote/reject
only read raw/<name>, so the documented approval path did not exist. They now
fall back to raw/needs-review/ (top level wins on a name clash; a symlinked
directory is refused) and promote drops the resolver's proposal keys.
Mutation-checked.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ingestion/internal/api/frontmatter.go

@@ -83,6 +83,18 @@ func (f *frontmatter) get(key string) string {
 	return ""
 }
 
+// drop removes every `key: value` line for key (nothing else), so a
+// machine-written key does not travel with a note into the wiki.
+func (f *frontmatter) drop(key string) {
+	kept := f.lines[:0]
+	for _, l := range f.lines {
+		if l.key != key {
+			kept = append(kept, l)
+		}
+	}
+	f.lines = kept
+}
+
 // set overrides the value for an existing key in place, or appends a new
 // `key: value` line when the key is absent.
 func (f *frontmatter) set(key, value string) {