feat(terminal): inline shell mode ($, $$)

[jom-sq]

Summary

Implements PR 5 from the Amp CLI feature parity plan.

Inline Shell Mode ($ / $$)

The Amp CLI supports $ prefix in the chat input to run shell commands with output added to agent context, and $$ for "incognito" mode where output is shown but NOT added to context. Our app previously only had a full PTY terminal via Ctrl+T.

How it works:

• Type $ ls -la → runs in thread workspace, shows output inline in chat
• Type $$ git status → runs incognito (output dimmed, not in agent context)
• Commands execute via the existing WebSocket connection with a 30s timeout and 1MB output buffer
• Shell results render with monospace styling, exit code badges, and incognito indicators
• A visual indicator appears in the input area while typing a $/$$ prefix, explaining the mode

Editor Prompt (removed)

The Ctrl+G / $EDITOR prompt feature was planned but removed after multiple attempts (Ctrl+G, Ctrl+E, Alt+E) all conflicted with browser or macOS default shortcuts. This is a limitation of the web environment vs the native CLI.

Changes

File	Change
shared/websocket.ts	Added shell_exec client and shell_result server message types
shared/validation.ts	Runtime validation for shell_exec messages
shared/validation.test.ts	Tests for shell_exec validation
server/websocket.ts	Shell command execution handler (30s timeout, 1MB buffer)
src/utils/parseMarkdown.ts	Extended Message type with shell result fields
src/components/terminal/useTerminalWebSocket.ts	sendShellExec() + shell_result handler
src/components/terminal/Terminal.tsx	$/$$ prefix detection in handleSendMessage
src/components/terminal/TerminalInput.tsx	Shell mode visual indicator
src/components/terminal/TerminalMessages.tsx	Shell result rendering component
src/styles/terminal.css	Shell result styles (monospace, exit code badges, dimmed incognito)

Testing

• pnpm check passes (format, lint, typecheck, build)
• pnpm test passes (227 tests)
• Manual: $ ls -la runs and shows output inline
• Manual: $$ git status runs incognito (dimmed output)