Redesign Atacama theme — fix flat neutral-grey light surfaces

[gregpriday]

Summary

The Atacama light theme is inspired by the Atacama Desert — arid, mineral, high-altitude neutral grey. The surface palette is intentionally stark and minimal, but this makes it the flattest-looking of all the light themes. Without enough visual hierarchy, the interface looks like a low-contrast grey document rather than a purposeful IDE.

Problem Statement

Atacama uses #F4F4F2 (canvas) and #EBEAE6 (sidebar) — near-white neutral greys with the faintest warm undertone. The problem is that neutrality in a light theme requires more careful tuning than a dark theme:

• surface-canvas: #F4F4F2 and surface-panel: #FAFAF8 are extremely close — panels barely float above the canvas. The elevated panel (#FFFFFF) is brighter but only by a small step.
• surface-grid: #E3E2DE and surface-sidebar: #EBEAE6 are nearly identical, meaning the panel grid (which should frame and separate panels) is almost indistinguishable from the sidebar and other surfaces.
• border-default: #D5D3CE is a barely-there warm grey that's almost invisible against surface-panel: #FAFAF8. With the derived border-subtle and border-divider being even fainter, the entire border system essentially disappears.
• The Canopy green accent #3F9366 pops strongly against these neutral surfaces — there's no supporting palette to bridge between the neutral surfaces and the vivid green, making it feel like a foreign color injection.
• activity-active: #1D9B5E is a slightly muted green — better adapted than the raw #22c55e, but still the only saturated element in an otherwise deliberately unsaturated theme.
• status-info: #1447A4 is a very saturated cobalt blue — the most vivid token in the theme. On the pale neutral canvas it's usable but feels over-injected.
• The overall theme looks like an unfinished "default system light mode" rather than a considered theme with personality.

Relevant code:

• shared/theme/themes.ts#L748-L810 — current Atacama token definitions
• e2e/core/core-light-theme-smoke.spec.ts — smoke test with contrast checks
• Issue Improve theme token coverage to fix washed-out light themes #3346 — token coverage improvements (foundation)

Desired Behavior

Atacama should feel like the high-altitude desert: mineral-white and pale stone with dry, cracked earth mid-tones and the faint blue of altitude. The theme can be clean and minimal — but it needs enough contrast in its surface stack and border system to give the interface structure. Specifically:

• The surface hierarchy should be legible: canvas → sidebar → panel → elevated panel should be clearly distinguishable steps.
• Borders should visibly separate components without being heavy or dark.
• The accent and status colors should feel intentional — like tools designed for a light neutral IDE, not transplanted from a dark theme.
• Status indicators and activity dots should be adapted for light mode: muted enough to not jump off the surface, vivid enough to communicate state.

Verification Workflow

1. Apply: await setAppTheme(window, "atacama").
2. Run getThemeChromeMetrics — verify smoke test checks pass.
3. Screenshot: full page plus close-ups of the sidebar, worktree dashboard, and a settings dialog.
4. AI evaluation: does the theme feel designed? Is there enough surface differentiation? Does it look washed out?
5. Iterate; npm run check.

Acceptance Criteria

• E2E smoke test passes for Atacama.
• Canvas, sidebar, panel, and grid are visually distinct — a user can identify the structural regions without looking at the code.
• border-default is visible against both panel and canvas backgrounds.
• The overall palette has a coherent identity (mineral/desert neutral) that is distinct from Svalbard (arctic blue) and Hokkaido (cool blue-grey).
• All E2E tests pass.

Dependencies

Depends on #3346 for improved border and overlay token overridability.

Edge Cases & Risks

• Terminal scheme pairing from PR feat(terminal): match terminal color scheme to app theme automatically #3345 — verify after changes.
• Atacama's syntax-operator and syntax-keyword are both set to #293D71 (same value) — this is likely a copy-paste error. The redesign should address this.

[gregpriday]

Terminal color scheme — review as part of redesign

The APP_THEME_TERMINAL_SCHEME_MAP currently maps atacama → atom-one-light (Atom One Light). As part of this theme redesign, review whether the terminal color scheme still pairs well with the updated app surfaces:

1. Evaluate the current pairing — after updating the surface/accent tokens, check whether Atom One Light still feels cohesive. If the surface palette shifts significantly, the terminal may look disconnected.
2. Research alternatives — search for well-known open-source terminal color schemes whose character matches the redesigned theme. Evaluate candidates for ANSI color legibility against the new surface background, not just aesthetic similarity.
3. Consider a bespoke scheme — if no existing scheme is a tight fit, create a dedicated one derived from the redesigned app tokens (like we did for Daintree via getTerminalThemeFromAppScheme). This gives the tightest visual integration.
4. Adapt rather than copy — if borrowing an open-source palette, adjust selection background, cursor, and bright variants so they harmonize with the app's surface/accent tokens.

Update APP_THEME_TERMINAL_SCHEME_MAP in src/config/terminalColorSchemes.ts and add any new scheme to the BUILT_IN_SCHEMES array. Update the test count in src/config/__tests__/terminalColorSchemes.test.ts if adding a new scheme.