Summary

Three issues making the TUI unusable on iTerm (and any terminal with a non-default background):

1. Themed backgrounds not applied

The theme system defines SURFACE.bgInput (#0f172a) and SURFACE.bg (#0b1020) but no component applies them. The entire UI renders with the terminal's default background, making input text invisible and the theme ineffective.

• PromptInput.tsx — add backgroundColor={SURFACE.bgInput} to the outer Box
• App.tsx — add SURFACE import and backgroundColor={SURFACE.bg} to root content layout
• ComposerArea.tsx — add SURFACE import and backgroundColor={SURFACE.bgInput} to wrapper Box

2. WCAG AA contrast failures on fg.faint and fg.meta

fg.faint failed WCAG on all 4 dark themes (ratios 1.63–2.56:1, need 4.5:1). fg.meta failed on midnight and was borderline on others. Dark theme bgElev was too close to bgInput for surface distinction.

3. ANSI dim causing invisible text across all UI components

The dim attribute (SGR 2) halves the brightness of the foreground color. On dark terminals, dimmed text without an explicit color uses the terminal default at half brightness — effectively invisible. This affects 22 components across the entire TUI.

Initial fix (earlier commits):

• ReasoningCard.tsx — replace dim with explicit FG.sub for card metadata
• ToolCard.tsx — replace conditional dim with explicit FG.faint/errColor
• chat.tsx — emit OSC 11 to set terminal default background, reset via OSC 111 on exit

Full fix (this commit): Replace every remaining dim prop across 22 UI components with explicit color={FG.faint} or conditional color logic:

• mcp-browse, AtMentionSuggestions, DiffApp, EditConfirm
• McpBrowser, McpHub, McpMarketplace
• PlanReviseConfirm, PlanStepList
• RecordView, ReplayApp, Select, Setup
• SlashArgPicker, SlashSuggestions, SplitDiff
• StatsPanel, Wizard, char-bar, ctx-breakdown
• markdown-view (SpanText ambientDim), primitives (Bar, ContextCell)

For conditional dim (e.g. dim={isDone}), replaced with conditional color logic (color={isDone ? FG.faint : originalColor}). The Bar component's dim prop was removed entirely — callers now pass the appropriate color directly.

Test plan

• Verify input area has a distinct themed background in iTerm
• Verify text is clearly readable against the new background
• Switch themes with /theme — backgrounds and text should change accordingly
• Verify border, placeholder, and faint text are visible with sufficient contrast
• Verify reasoning card metadata ("◆ reasoning · 20 tok") is readable
• Verify tool card preview lines are readable
• Verify no white/empty areas below content in iTerm
• Verify all UI components (slash suggestions, session picker, MCP browser, etc.) have readable text
• Run npm run verify (lint + typecheck + tests)