fix(ui): make delete-project dialog readable under the paper theme

[CatJuly]

Summary

Switching to the paper theme and clicking delete on a project produced an unreadable confirmation dialog — the title and body text were invisible against the panel.

Root cause

ProjectSelector.tsx painted the dialog panel with:

background: 'var(--bg-surface, #1e1e2e)'

--bg-surface is not defined by any stylesheet in the project — a scan of every var(--token) reference against every theme block confirms it, along with --bg-primary, are the only two undefined tokens. So all seven themes fell through to the hardcoded dark #1e1e2e and the panel never tracked the active palette.

This stayed invisible under the six dark themes, whose --text is light and therefore still contrasted fine against a dark panel. The paper theme is the only light palette — its --text is #1e293b, which put dark text on the dark panel at roughly 1.05:1 contrast.

It also explains the exact shape of the symptom: Cancel stayed faintly legible because .pill-btn uses --text-secondary, and Delete stayed fully legible because it hardcodes color: #fff over a red fill. Only the title and body, which inherit --text, disappeared.

Fix

• Panel background → var(--bg-elevated), so it follows the active theme (#ffffff under paper, #141b2b under midnight, etc.)
• Title and body get explicit --text / --text-secondary instead of inherited color plus opacity: 0.7 — dimming by opacity is equally unreliable over a light surface
• Added a --border outline so the now-white panel still reads as a distinct layer above the scrim

Fixing the token rather than adding a .theme-paper override keeps the next light theme from hitting the same trap.

Effect on other themes

All seven themes now resolve the panel from their own palette. The six dark themes shift only slightly (#1e1e2e to e.g. #141b2b) since they were already close to the hardcoded value — they go from coincidentally readable to consistently themed.

Testing

• npm run typecheck passes
• Opened the dialog by hand under all seven themes; paper is now readable and the other six are unchanged in practice
• frontend_dist rebuilt and included, matching the convention in feat: harden company resume, external sessions, and Office UI i18n #9 and 全系统的状态刷新没有对齐，必须强制刷新 #11

Note

There is a second instance of this token class not touched here: kanban/kanban.css:922 uses color-mix(in srgb, var(--bg-primary) 80%, transparent) where --bg-primary is undefined and has no fallback, so that whole background declaration is dropped at compute time. Left out to keep this PR scoped to the reported bug — happy to send it separately.