fix(insights): let "Re-run analysis" reach a benched provider

The on-demand briefing (POST /api/insights/generate) runs through the
briefing chokepoint, which named its chain walk "job" for the background
share of the day's ceiling. Since background work leaves out a provider the
health ledger benched, a person pressing "Re-run analysis" got no request at
all: the call failed with a connection refusal that never happened, and a
refused credential was never reported back.

The chain runners now take the walk apart from the budget surface: a call
can be rationed as a job and still have a person waiting on it
(interactive). runBriefingCompletion takes the flag and the on-demand
route's calls (the first pass and the grounding retry) pass it, so they keep
the job share and walk a benched provider at the tail, as background-bench
promises for interactive walks. Every other job-surface caller is a worker
or is enqueued; the status, narrative and warm routes only read and queue,
and document reads and lab scans resolve a single provider without a chain.

Refs #1279

src/__tests__/baselines/version-stamp-comments.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Comment lines that open with a release version, per file under src/. Maintained by src/__tests__/version-stamp-ratchet.test.ts.",
   "count": 2897,
-  "total": 9263,
+  "total": 9262,
   "entries": {
     "__tests__/account-payload-consumer-guard.test.ts": 2,
     "__tests__/acting-account-boundary-guard.test.ts": 7,
@@ -1783,7 +1783,7 @@
     "lib/ai/prompts/weight.ts": 2,
     "lib/ai/provider-chain.ts": 1,
     "lib/ai/provider-health-ledger.ts": 3,
-    "lib/ai/provider-runner.ts": 15,
+    "lib/ai/provider-runner.ts": 14,
     "lib/ai/provider.ts": 10,
     "lib/ai/reasoning/__tests__/controls.test.ts": 1,
     "lib/ai/reasoning/controls.ts": 2,