UX: Redraw screen on oclite boot — cursor at bottom

[randomm]

Problem

When oclite boots, previous terminal output is visible above the header. The new session starts mid-screen with no visual separation. Users see stale output from prior runs mixed with the fresh oclite header.

Solution

Clear the screen on boot to give a clean start.

Boot sequence:

1. \x1b[2J\x1b[H — Clear screen + cursor to home (top-left)
2. Render header: oclite v0.1.0
3. Show Setting up environment... with spinner while backend bootstraps
4. Once bootstrap completes: clear the setup message, show Ready, render prompt with visible cursor

Important: Do NOT use alternate screen buffer (\x1b[?1049h) — this kills scrollback history. Use main buffer clear instead.

Research Findings (from exploration of Lazygit, Aider, Claude Code, htop)

• Chat TUIs (Claude Code, Aider) never use alternate screen — users need scrollback
• Editors/monitors (Lazygit, htop) do use alternate screen — but they don't need scrollback
• Recommended: main buffer clear (\x1b[2J) for clean start while preserving future scrollback
• Handle SIGWINCH for terminal resize

Related

• UX: Show initialization progress and hide cursor until backend ready #57 (no initialization feedback during MCP bootstrap)
• [Architecture] oclite: Live Block rendering with log-update for tools, tasks, and todos #82 (Live Block architecture)

[randomm]

Research Findings: Full-Screen Boot Patterns

How production tools handle it

Tool	Alternate Screen?	Approach
Claude Code	❌ No	Main buffer, preserves scrollback
Aider	❌ No	prompt_toolkit with full_screen: false
Lazygit/htop/btop	✅ Yes	Alternate screen — but they're NOT chat TUIs
Vim/Neovim	✅ Yes	Alternate screen — editor, not chat

Decision: Main Buffer, Push-Down Pattern

Never use alternate screen — chat users need scrollback to review conversation history after exit.

Recommended boot sequence:

1. Clear current line only: \r\x1b[K] (preserve everything above)
2. Write rows - 3 newlines to push cursor to bottom of terminal
3. Render header at position rows - 2
4. Render prompt at position rows
5. Handle SIGWINCH to re-anchor on resize

Key ANSI sequences:

• \r\x1b[K — clear current line (clean start)
• \x1b[{row};1H — position cursor at specific row
• \x1b[{n}A — move cursor up n lines
• \x1b[s / \x1b[u — save/restore cursor position

Anti-patterns (confirmed by research)

• ❌ \x1b[?1049h alternate screen — kills scrollback
• ❌ \x1b[2J aggressive clear — loses terminal history
• ❌ \x1b[1;Nr scroll regions — already tried and reverted ([Architecture] oclite: Revert scroll region layout, adopt append-only output model #73)
• ❌ Hardcoded terminal dimensions

Implementation Notes

• Store messages as line arrays, re-render visible portion on resize
• process.stdout.rows and process.stdout.columns for dimensions
• process.on('SIGWINCH', rerender) for resize handling

[randomm]

Fixed in 369a296 — screen clears on boot with spinner covering init