[M4] TextFrame: show text preview in nav-links instead of raw IDs

[Korede-TA]

Goal

Nav-links in the TextFrame node navigation (parent chain, children list) currently display raw node IDs. Replace these with human-readable text previews using the existing deriveLabel utility. IDs can still be shown as a secondary detail in the text-focus view.

What to do

• In TextFrame.tsx, wherever nav-link labels are rendered (parent chain, child list buttons), replace node.id with deriveLabel(node):
  • deriveLabel priority: properties.title → properties.source (filename) → first 80 chars of node.text → fallback to node.id
• For the child list: show derived label as the button text; show node.id as title attribute (visible on hover) and optionally as a secondary line in the text-focus view
• For the parent chain breadcrumb: same — derived label as display text, ID in tooltip
• Keep the type-badge (document/chunk/expression) next to each label for quick scanning

Relates to

• [M5] akb_adapter: emit title and source as node properties #44 — Python adapter must emit properties.title / properties.source for this to show non-ID labels on document nodes
• [M4] Breadcrumb nav + browser history (level/focus changes) #25 — breadcrumb nav browser history integration should use the same label logic

Acceptance criteria

• Nav-links display meaningful text (title, filename, or text excerpt) instead of raw UUIDs
• IDs remain accessible (hover tooltip or secondary text in text-focus view)
• Works gracefully when no title/text is available (falls back to ID silently)