Polish pass 3: drop left-accent bar, restyle Archived as nav item

[blove]

Summary

• Active thread + project list items no longer show the asymmetric left-side accent bar (`box-shadow: inset 2px 0 0 ...`). Active state is now indicated only by `surface-alt` background + `font-weight: 500` — symmetric, calmer.
• "Archived" disclosure restyled from a faded 11px uppercase label to a proper sidenav nav item: `padding: 8px 12px`, `border-radius: 8px`, `font-size: 14px`, full text color, hover lifts to `surface-alt` — visually consistent with the Search action.
• Archived thread list uses the same `` primitive as Recent so item rendering is pixel-identical.
• @ngaf/* 0.0.39.

Test plan

• `pnpm nx test chat` — 775 tests pass
• `pnpm nx test examples-chat-angular` — 17 tests pass
• Local chrome-mcp verify: archived a thread → archived list item computed styles match recent list item exactly (`match: true`); active item box-shadow gone; Archived header matches Search nav-item geometry
• Canonical demo redeploys; both fixes live on demo.cacheplane.ai

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
cacheplane	Ready	Preview, Comment	May 18, 2026 4:58pm