feat: sidebar hierarchy tree-line connectors

[aterrylu]

Summary

• Add CSS-drawn tree-line connectors (├─/└─) to the sidebar hierarchy view, giving a clear visual trace of agent parent-child relationships
• Compact spacing (10px indent, 5px arm) to preserve sidebar width for long agent names
• Guide lines recursively aligned with parent status icon centers at every depth
• Preserves existing colored left border on parent nodes (blue=expanded, dim=collapsed)
• Downward connector from parent icon to children, hidden when group is collapsed

Design

Dispatcher
  TeamLead@autonomOS          ← blue left bar (has reports)
  ├─ CronDesign@autonomOS     ← compact branch connector
  ├─ MultiProvider@autonomOS
  └─ TreeLines@autonomOS      ← elbow connector (last child)
TeamLead@homelab              ← blue left bar
  └─ HW-Inventory@homelab
TeamLead@workflow

Key decisions:

• No connectors at root level (depth 0) — only children get tree lines
• Recursive guideX/treePaddingLeft functions align guides with parent icon centers rather than using a fixed linear formula
• TreeLineGuides component renders as a pointer-events-none overlay with z-index: 1
• Exited/stopped rows wrapped in a borderless container for correct guide alignment (avoids 3px CSS border offset)

Test plan

• make check passes (biome lint + tsc + 70 tests)
• Visual verification in dev server (hierarchy view with multiple nesting levels)
• Expand/collapse groups — connectors appear/disappear correctly
• Colored left border preserved on parent nodes
• Flat view unaffected (tree lines only render in hierarchy mode)
• All three themes verified (Midnight dark theme tested, colors use page.statusFg)

🤖 Generated with Claude Code

[nox-0x]

Solid implementation of tree-line connectors for the hierarchy view. The recursive geometry calculations (guideX / treePaddingLeft) are well-reasoned and produce consistent alignment with parent icon centers across all depth levels. ancestorIsLast propagation is correct, TreeLineGuides handles the last-child elbow vs branch case properly, and the pointer-events-none overlay avoids interaction conflicts. No critical issues found — LGTM ✅

[nox-0x]

Reviewed the full diff. The geometry functions (guideX, treePaddingLeft) are correctly recursive — icon center alignment is consistent at every depth. ancestorIsLast propagation is logically sound (i > 0 guard correctly skips depth-0 ancestor level in the reduce). The pointer-events-none overlay with zIndex:1 is safe, and indent={0} with paddingLeftOverride is the right split for SessionRow. No critical or blocking issues. LGTM ✅

[nox-0x]

LGTM ✅