fix(claude): hide pasted-content transcript wrappers

[Yoonwoo-Ha]

Problem

Claude persists terminal paste input inside a native <pasted_content id="…"> transcript envelope. Claude's TUI hides that metadata, but ChatMux rendered the raw string. Markdown treated the opening marker as HTML while exposing the invalid attribute-bearing closing marker as visible text.

Changes

• unwrap only complete Claude pasted-content blocks whose opening and closing IDs match
• leave partial, malformed, and mismatched lookalikes unchanged
• apply the same user-visible normalization to chat history and conversation search
• cover the observed transcript shape, multiple blocks, mismatched IDs, and provider message normalization

Verification

• replayed the observed Topk-Design transcript row: only the Korean prompt remains and no wrapper text survives
• focused Claude provider tests: 4 passed
• npm run verify
  • server tests: 1,850 passed
  • real tmux/PTY tests: 50 passed
  • client tests: 731 passed
  • typecheck, lint, identity, Rust checks, and production build passed