Speaker corrections: rename / merge / reassign + voice learning

Native editor to fix speaker-ID errors after transcription (modeled on recap-relay's
correction UX): rename a speaker in the legend, merge two speakers, or reassign an
individual transcript line. Saving rewrites speakers.json, re-renders transcript.md +
recap.html, and updates the voiceprint memory — so a correction compounds: naming an
"Unknown" speaker teaches that voice for future calls.

- SpeakerEditing (pure, tested): replaceSpeaker (rename = merge-onto-existing),
  reassign, netNameMap (compose ops), and remap (apply a name map to a recap's
  structured fields + whole-word free text, so summaries/extras update without re-LLM).
- RecapEditModel (@MainActor): loads speakers.json (+ optional recap.json +
  cluster_fingerprints.json); on save writes the resolved speakers.json, re-renders,
  and reconciles voiceprints — merge keeps the survivor's print; rename/name-an-Unknown
  enrolls the cluster's fingerprint under the new name.
- TranscriptEditorView (SwiftUI) + EditorWindow (AppKit window for the LSUIElement app);
  menu gains "Edit speakers".
- Pipeline now persists cluster_fingerprints.json (every cluster incl. Unknown) and
  recap.json (RecapFile) so the editor can learn voices + re-render offline.
- RecapModels made Codable; TranscriptAssembler exposes allFingerprints;
  VoiceprintStore gains enroll() + merge().

52/52 XCTest (6 new, incl. a full rename→artifacts→voiceprint round-trip on disk).

Ten31Transcripts/Session/TranscriptPipeline.swift

@@ -97,6 +97,13 @@ final class TranscriptPipeline {
 
         let assembled = TranscriptAssembler.assemble(sessionId: sessionId, app: app, chunks: results)
         try assembled.speakersFile.write(to: sessionFolder.appendingPathComponent("speakers.json"))
+        // Persist every cluster's voiceprint (incl. Unknown) so the speaker editor can
+        // teach the store a voice when the user renames an Unknown to a real name.
+        if !assembled.allFingerprints.isEmpty,
+           let data = try? JSONSerialization.data(withJSONObject: assembled.allFingerprints.mapValues { $0.map(Double.init) },
+                                                  options: [.sortedKeys]) {
+            try? data.write(to: sessionFolder.appendingPathComponent("cluster_fingerprints.json"))
+        }
         return assembled.speakersFile
     }