connect: full-width composer that wraps, readline shortcuts, and a live model list

[hbrooks]

Summary

Seven papercuts in the multi-session UI's new-session pane and nav bar.

• Heading now asks "What are we shipping today?" instead of "What would you like to do?"
• Full-width input: the pane carried a paddingLeft={1} that inset the composer's rules one column from the header's and the nav's. Removed; the rows inside carry their own indents.
• Wrapping: a long prompt truncated and ran off the right edge. Now wrap="wrap" against an explicit width, so it flows onto the next row and the box grows downward into the spacer above.
• Model list from the API: the picker's options were hardcoded and had gone stale (no Opus 5, and "Default" still claimed Opus 4.8). Now fetched from GET /v1/models, so it tracks the server registry instead of drifting each time we enable a model. An older server without that route falls back to a built-in list.
• Readline shortcuts in both text inputs (the chat composer and the new-session prompt) via a new shared src/lib/editing.ts: option/ctrl+arrows and meta+b/f hop a word, ctrl+a/e reach the line edges, option+backspace and ctrl+w kill a word, ctrl+u/k kill to the line edges. cmd+arrows never reach the process (macOS terminals keep the command modifier for themselves), so ctrl+a/e stand in for it.
• Nav dividers: vertical rules between session cells, so the bar reads as discrete sessions rather than one run of text.
• Nav new-session button is pinned at its full label width ("+ New session", never a truncated "+ Ne…"). A crowded bar drops session cells instead, which the "N more" tail already accounts for.

Depends on a backend change

GET /v1/models does not exist yet. /models exists but is a dashboard-cookie route the CLI's bearer token cannot call, so this PR needs the companion v1_router.py change (reusing the models router's supported_models()) before the picker reads live data. Until then the fallback list applies; I verified it matches the server registry exactly, Opus 5 and the default flag included.

Test plan

• vitest run — 298 pass, including new coverage for composerModelOptions (server order, default naming, empty fallback) and all of applyEditShortcut
• tsc --noEmit clean
• Drove the TUI in tmux: heading, full-width rules, nav dividers, and the model picker selecting Opus 5
• Typed a 130-char prompt and watched it wrap rather than run off-screen
• Confirmed option+left, ctrl+a, ctrl+e, and ctrl+w move and kill text (caret position read from capture-pane -e)
• Nav checked at 40/60/80/120/160 columns: the new-session button stays whole and cells drop; 40 previously wrapped the bar onto an extra row
• Not UI-verified: the chat composer's shortcuts. Every session in my list is watch-only (laptop-synced or Slack-owned), so no composer was reachable. It calls the same helper driven live in the new-session pane, and the helper is unit-tested, but I did not observe it there.