Vim refactor: migrate Watchlist page to declarative nav (#104)

[binarypath]

Parent: #104

The /watchlist page has h/l for switching between watchlists, j/k for navigating symbols, and the d/y/p row-ops (cut/yank/paste) buffer. Bespoke handler in vimHandlers.watchlist.

Scope

• Watchlists row (the tabs strip) gets data-vim-row + per-tab data-vim-item. h/l between watchlists.
• Symbol rows get nested data-vim-row (each symbol is its own row of cells).
• Preserve d/y/p semantics via the per-view handler's deleteSelected / yankSelected / pasteSelected falling through.

Acceptance

• h/l switches watchlists.
• j/k navigates symbol rows.
• d cuts to buffer, y opens copy picker, p pastes to active watchlist.
• gg / G work.