## Summary
Rename the "Usefulness" UI label to "Traffic share", add hover tooltips
for both Traffic share and Bridge score, and introduce a new
`traffic_share_score` field on `/api/nodes` (alongside the legacy
`usefulness_score`, kept for API back-compat).
Closes#1456.
## Why
The "Usefulness" label implied a composite score that doesn't exist yet
— only the Traffic-share axis (axis 1 of 4 from #672) and the Bridge
axis (axis 2 of 4 from #1275) are wired today. A node with low traffic
but critical structural position read as "not useful" — exactly wrong.
Neither score had a tooltip explaining what it measured.
## Changes
### Frontend (`public/nodes.js`)
- Visible label `Usefulness` → `Traffic share` (with ⓘ glyph)
- Tooltip explains traffic-share semantics, cross-references Bridge for
structural importance, points at #672 for the 4-axis roadmap
- Bridge row gets a parallel ⓘ glyph and a tooltip naming "betweenness
centrality" + the "quiet but irreplaceable chokepoint" interpretation
- Prefers new `traffic_share_score` with graceful fallback to legacy
`usefulness_score`
### Backend (`cmd/server/routes.go`)
- `/api/nodes` and `/api/nodes/{pubkey}` now emit BOTH
`usefulness_score` (kept for API compat) AND `traffic_share_score` (new
canonical name), populated with the same value
- Inline comment documents the deprecation path: when the #672 composite
ships, `usefulness_score` becomes the composite and
`traffic_share_score` keeps the per-axis value
## Tests
- `test-issue-1456-score-labels.js` — file-grep pins on `nodes.js`
(label, tooltip fragments, percent formatting, dual-field read with
fallback)
- `cmd/server/traffic_share_score_test.go` — `/api/nodes` +
`/api/nodes/{pk}` responses contain both fields with equal values
TDD: red commit (`8bd235a0`) added failing tests; green commit
(`c4d3aee5`) implemented. `go test ./cmd/server/...` passes (47s).
## Out of scope
- Renaming the backend field (would break consumers)
- Wiring axes 3 (Coverage) and 4 (Redundancy) — tracked in #672
- Changing the score calculation
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Co-authored-by: clawbot <bot@openclaw.local>
