feat: refine source sentences and add copy-id buttons on review rows

[Rassl]

Follow-ups to the merge-context panel (#396):

• send edge_type as the stringified list the backend's ast.literal_eval expects — the natural repeated-key form 400s
• cards ordered sources-first/canonical-last from action_payload direction, matching the columns above (subject_ids order is fingerprint-sorted)
• excerpts come only from prose properties (text > transcript > description

  summary) — never from name/title labels — and are windowed to a few
  words around the subject's name, matched word-by-word with prefix stemming so inflections hit; literal \n and \uXXXX escapes in stored tweets are decoded; sources actually containing the name rank first and no-match fallbacks render dimmed with an explanatory tooltip

• the name's words are highlighted inside each excerpt
• every subject row in an expanded review gets a small copy-node-id button