v0.7.1: fix console blank page (span_ids) + UI rename (Agent Traces / HTTP Logs)

[vaderyang]

What

Patch release v0.7.1 — fixes the production console blank-page regression
introduced by the v0.7.0 OTel rename, and aligns the UI vocabulary with the
trace/span model.

Fix (P0) — blank page

The v0.7.0 OTel rename made the traces API serialize span_ids (formerly
call_ids) and updated the API-path hooks — but the AgentTurnDetail type and
the agent-breakdown component were missed and still read call_ids. At runtime
turn.call_ids is undefined, so turn.call_ids.length throws TypeError: undefined is not an object. With no React error boundary, that render throw
blanks the entire console whenever an agent trace detail is opened.

The soak gates exercise backend invariants, not frontend rendering, and the stale
TS type kept tsc green — so it reached production.

Fix: align the type + component to span_ids, guard the access with ?. so a
missing field degrades to "0 calls" instead of a white screen. Audited the rest
of the frontend↔backend response fields — span_ids was the only field-level
rename, all hooks already call /api/traces* + /api/spans*, and the
agent_turns_open metric name still matches.

Rename — UI vocabulary

A trace is one agent interaction; a step within it is a turn/span. Renamed
user-visible labels accordingly:

• "Agent Turns" → "Agent Traces", "HTTP Exchanges" → "HTTP Logs"
• nav, detail titles, overview gauge, "Trace ID" metadata, empty/error states,
  SFT export tooltip, distribution chart legend

Left unchanged: backend metric names, pipeline stage/metric-group names, route
paths, code identifiers, and the SFT-domain term "multi-turn trajectory".

Version

VERSION SSOT + Cargo.toml + package.json + Cargo.lock → 0.7.1; CHANGELOG [0.7.1].

Release path

After merge, main runs ci → deploy-staging → {staging-soak, ebpf-soak}. Once
both stamps land, tag v0.7.1 on that commit to let release.yml cut the release;
deploy-prod gates on manual approval.

Verification

cargo check -p heron, console tsc -b + build all pass.