AI cost/ROI page: pricing table, cost per call, Cost tab, ROI endpoint

- templates/web/pricing.py: pricing table with source and as-of date; cost_for_call
  (input rate + (output + thinking) at output rate, long-context above threshold;
  unknown model raises naming the known models).
- Cost tab: coverage pill, total/this-month/tokens tiles, month-by-month table,
  per-run tokens and cost ("not priced", never $0), by-hand panel with editable
  assumptions labelled as such.
- Contract: RoiRun and GET /roi; optional GET /models and POST /runs/{id}/retry.
- SKILL.md: cost page wiring, model picker and retry-on-other-model as optional sections.
- Tests: test_pricing.py self-check, page_check_ai/test_ai_cost.py.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

rpa-dashboard-ai/templates/web/src/ai.ts

@@ -23,6 +23,19 @@ export type ReviewRow = {
   corrected_value: string | null
 }
 
+/** One run on the cost page. total_cost is null when the run recorded no token usage (unpriced). */
+export type RoiRun = {
+  job_id: string
+  document: string
+  created_at: string // ISO, UTC
+  model: string
+  input_tokens: number | null
+  output_tokens: number | null
+  thinking_tokens: number | null
+  total_cost: number | null // USD
+}
+export type Pricing = { source: string; as_of: string }
+
 export const BUSY: RunStatus[] = ['queued', 'running'] // polled every 1.5s while in one of these
 
 /** Legend order, label, and the colour token. Band colours are semantic: never on buttons or headings. */
@@ -53,5 +66,6 @@ export const ai = {
     req<ReviewRow>(`/review/${rowId}`, { method: 'PATCH', body: JSON.stringify(body) }),
   verifyRemaining: (id: string) => req<{ verified: number }>(`/runs/${id}/verify-remaining`, { method: 'POST' }),
   approve: (id: string) => req<{ ok: boolean }>(`/runs/${id}/approve`, { method: 'POST' }),
+  roi: () => req<{ runs: RoiRun[]; pricing: Pricing }>('/roi'),
   documentUrl: (id: string) => `${API_BASE}/runs/${id}/document`,
 }