fix(pipeline,api,wing): never archive a note as processed when nothing was ingested; titles do not merge sources; ties prefer the page on disk (review of #211, pass 3)

- in a wing, an ingest that writes no source page is an error: the note goes to
  raw/failed with the warnings in log.md instead of leaving the inbox as
  'processed' (model returned [], only invalid types, only clashing entities)
- the wing's source path is deterministic, so Resolve no longer redirects a
  source onto another note's page because the model gave both the same title
  ('Home'); that overwrote the hash and the text
- a batch tie between concept and entity prefers the page already on disk, so
  its update is not lost; the wing's own source page keeps its slug even when a
  foreign page shares it
- brain_pending lists an unreadable (over-cap) note with the reason instead of
  dropping it; the client filter's 4 KiB match-span limit is documented
Each has a test that fails without it (mutation-checked).

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

ingestion/internal/pipeline/resolve.go

@@ -32,6 +32,13 @@ func Resolve(proposed []wiki.Page, inventory map[wiki.PageType][]wiki.Entry) []w
 
 	out := make([]wiki.Page, 0, len(proposed))
 	for _, page := range proposed {
+		if isWingSourcePath(page.Path) {
+			// In a wing the source's path is its filename-derived slug. Matching
+			// by TITLE would merge two different notes the model happened to
+			// title alike ("Home", "Untitled") into one page.
+			out = append(out, page)
+			continue
+		}
 		pt := pageTypeOf(page)
 		title := extractTitle(page.Content)
 		k := key{pt: pt, normalized: normalizeTitle(title)}
@@ -97,3 +104,9 @@ func extractTitle(content string) string {
 	}
 	return ""
 }
+
+// isWingSourcePath reports whether path is wiki/<wing>/sources/<slug>.md.
+func isWingSourcePath(path string) bool {
+	parts := strings.Split(filepath.ToSlash(path), "/")
+	return len(parts) == 4 && parts[0] == "wiki" && parts[2] == "sources"
+}