Orbit UI review: 6-phase fix plan before alpha release

Outcome of an agent-driven UI/UX review on \`nekrut:notebook-rewire-pure-md\`. Plan is to land 6 phases as separate commits, ordered by impact and shipability. Each phase independent — pause between any two without leaving the branch in a broken state.

## Phase 1 — Theme integrity

Highest visual impact. Modal buttons today fall back to native OS controls because \`.plan-btn\` has no base style; brand colors leak blue in several places.

- [ ] Add base \`.plan-btn\` rule in \`styles.css\` near line 1525 with \`.primary\` / \`.execute\` / \`.danger\` variants
- [ ] Drop hard-coded blue fallbacks (lines 1736, 1801, 1880, 1901)
- [ ] Fix focused-input box-shadow at lines 1313, 1513 (blue → gold)
- [ ] Replace \`color: gold\` literals at 626, 1452 with \`var(--accent)\`
- [ ] Replace \`#c8a200\` at 950 with \`var(--galaxy-gold-dark)\`
- [ ] Drop unused \`--state-ok-border\` / \`--state-error-border\` (lines 50–53)

~50 lines, one file.

## Phase 2 — Modal escape hatches + Galaxy validation + UX traps

Stop alpha testers from getting stuck or persisting half-filled config.

- [ ] Welcome screen: add \"Skip — set up later\" button + Esc binding
- [ ] Galaxy form: require both URL+key or neither; disable Save (block) when half-filled
- [ ] Skills \"Remove\": wrap in \`confirm(...)\`
- [ ] Replace \`addUserMessage(\"[system] Preferences saved...\")\` with \`addInfoMessage\`
- [ ] \`agent-status\` badge: clickable when stuck \`connecting…\` or \`error\`, opens Preferences

~55 lines.

## Phase 3 — Activity-tab + chat ergonomics

- [ ] \`revealActivityForTurn\`: only auto-switch tab when pane was *collapsed*; if expanded with non-default tab, leave alone
- [ ] \`/cost\` and \`/summarize\`: leading info card so tester sees something queued
- [ ] \`#input\` placeholder → \"Ask for a plan, drop a file path, or type / for commands\"
- [ ] Merge three quick info cards after \`/new\` into one
- [ ] proc-monitor \`\` initial \"(no data yet)\" row
- [ ] \`#switch-dir-link\` listener stacking: switch to event delegation on \`messagesEl\`

~35 lines.

## Phase 4 — Responsive layout (validate breakpoints first)

Resize Orbit live to find right breakpoints, **then**:

- [ ] \`@media (max-width: ~900 px)\` auto-applies \`body.files-collapsed\`
- [ ] \`@media (max-width: ~700 px)\` auto-applies \`body.artifact-collapsed\`
- [ ] \`.pane-tab\` \`min-width: 0\` + \`.pane-tab-label\` ellipsis
- [ ] Empty-state padding inside \`#notebook-view\` (drop conflict between 16 px pane padding + 40 px empty padding)
- [ ] \`.pane-tabs\` left-align (was \`justify-content: center\`)
- [ ] \`.pane-tab-close\` 16px → 20px hit target
- [ ] \`.prompt-num\` \`min-width: 28px\` for 5-digit overflow
- [ ] \`#proc-monitor-count\` hide/grey at zero

~45 lines CSS.

## Phase 5 — Accessibility

- [ ] \`aria-label\` on icon-only buttons (\`#send-btn\`, \`#abort-btn\`, \`#files-toggle\`, \`#artifact-toggle\`, \`#cwd-change\`, \`#galaxy-status\`)
- [ ] Convert \`#galaxy-status\` from \`

Start with styles.css and index.html, then trace the named UI elements and handlers for each phase in Orbit. Work through the six independently committable phases, validating responsive breakpoints live and restarting before accessibility checks. Done means every checklist item is addressed, Orbit smoke tests pass, and the alpha UI no longer exhibits the listed theme, modal, responsive, accessibility, or documentation issues.

Written by the indexing model from the issue text.