feat(initial-implementation): phase 0 - scraping spike findings

Anonymous scraping confirmed feasible for marathonbet.by — site is fully SSR
(nginx), no Cloudflare or JS challenge. HttpClient + AngleSharp + Polly v8 is
sufficient; Playwright not required (kept as a future-flag).

Spike outputs:
- spike/SCRAPE_FINDINGS.md  — page rendering, URL templates, anti-bot, rate
  limits, recommended scraping strategy for Phase 3.
- spike/SCHEMA_DRAFT.md     — customer-spec field → DOM selector mapping for
  Match + Period-N scope across football/basketball/tennis (hockey TBD).

Phase 1+ handoff captured in subplan + CLAUDE.md. Critical Phase 8 finding:
no public results endpoint at /su/results — phase 8 must switch to polling
event-detail until eventJsonInfo.matchIsComplete=true (deviation flagged).

Reviewer notes addressed:
- Period market outcome codes corrected to RN_H/RN_D/RN_A (not 1/draw/3) and
  market name vocabulary clarified per-sport in SCHEMA_DRAFT §3.1.
- results-page.html capture added to file list with caveat about live-landing
  score-state and unsampled hockey selectors.

plans/initial-implementation/CONTEXT.md

@@ -55,7 +55,21 @@ with scraping research, no implementation.
 
 ## Failed Approaches
 
-(none yet — phases not started)
+- **Public results / archive endpoint** — does NOT exist. Tested
+  `https://www.marathonbet.by/su/results`, `/su/results/`, `/su/results.htm` —
+  all return HTTP 404. No `/archive`, `/history` links anywhere in the public
+  HTML either. **Phase 8 deviation:** the Results loader cannot back-fill from
+  an archive — it must poll each event detail page until
+  `eventJsonInfo.matchIsComplete=true` and snapshot `resultDescription` at that
+  moment. Phase 8 implementer must revise the subplan accordingly.
+- **JSONP `/su/liveupdate/popular/` endpoint** — exposes only refresh signals
+  (`{"modified":[{"type":"refreshPage"}],"updated":<ts>}`), not actual odds. Cannot
+  be used as a JSON odds source. Use it only as a "something changed" hint to
+  trigger a full event-detail re-scrape.
+- **Anonymous WebSocket (STOMP)** at `/su/websocket/endpoint` is documented in
+  `initData.stomp` but appears to require an authenticated session
+  (`PUNTER-SESSION-HASH` cookie); we did not test it but the customer's anonymous
+  scraping constraint makes it unsuitable anyway.
 
 ## Review Findings Log
 
@@ -65,7 +79,7 @@ with scraping research, no implementation.
 
 | Phase | Agent | Model | Test Writer | Parallel | Notes |
 |---|---|---|---|---|---|
-| Phase 0 | phase-implementer | Sonnet 4.6 | ⏭️ Skipped (research only) | — | Throwaway probe; outputs SCRAPE_FINDINGS.md only |
+| Phase 0 | phase-implementer | Opus | ⏭️ Skipped (research only) | — | ✅ Done 2026-05-05. Outputs: spike/SCRAPE_FINDINGS.md + spike/SCHEMA_DRAFT.md + 7 local fixtures. Anonymous scraping confirmed feasible; HttpClient+AngleSharp recommended; no Playwright needed; no public results page found (Phase 8 deviation noted). |
 | Phase 1 | phase-implementer | Sonnet 4.6 | ⏭️ Skipped (Big Bang) | — | — |
 | Phase 2 | phase-implementer | Sonnet 4.6 | ⏭️ Skipped (Big Bang) | ✅ With 3 + 5 | — |
 | Phase 3 | phase-implementer | Sonnet 4.6 | ⏭️ Skipped (Big Bang) | ✅ With 2 + 5 | — |
@@ -87,4 +101,39 @@ with scraping research, no implementation.
 
 ## Implementation Notes
 
-(populated as we work)
+### Phase 0 (Scraping spike, 2026-05-05)
+
+- **Anonymous scraping is feasible** from a non-Belarus IP. No Cloudflare, no JS
+  challenge, no UA filtering observed. `Server: nginx`. Standard cookies only.
+- **Site is fully SSR.** All needed data (event grid, full odds, breadcrumbs,
+  period markets) is in the raw HTML. No SPA hydration required.
+- **Recommended scraper stack: HttpClient + AngleSharp + Polly v8.** Playwright is
+  not required for read-only scraping — keep it as an optional fallback flag
+  (`Scraping:UsePlaywright`) for future-proofing only.
+- **Polling cadence:** site itself polls live updates every 3 s; for our analyzer,
+  pre-match 30 s and live 5–10 s is sufficient.
+- **Rate-limit:** 5 sequential requests at 1 req/s pacing all returned 200 in <1 s,
+  no throttling. Recommend default `RequestsPerSecond=1`, `MaxConcurrent=4`.
+- **Sport ID semantics:** customer's "Sport_Code = 6" (Basketball) maps to
+  `data-sport-treeId="6"` in the breadcrumb-canonical sport listing
+  (`/su/betting/Basketball+-+6`). Some sports also have a separate "category tree
+  ID" used inside the live grouping (e.g., 45356 for Basketball-live) — ignore
+  those, use only the canonical breadcrumb ID.
+- **Selection key format:** `<eventId>@<MarketName>{LineIndex?}.<Outcome>`. The
+  market name is sport-specific (`Match_Result`, `1st_Half_Result`, `Total_Goals`,
+  `Total_Points`, `Total_Games`, `To_Win_Match_With_Handicap`, etc.). Total
+  thresholds are encoded in the outcome (`Under_3.5`, `Over_213.5`). Handicap
+  values are NOT in the key — they're in `<span class="middle-simple">` text.
+- **Tennis has no Draw outcome** — domain `Bet_Match_Draw` must be nullable.
+- **Date display ambiguity:** listing shows `HH:MM` (today) or `DD <ru-month> HH:MM`
+  (future). Anchor the parser on `initData.serverTime` (Moscow TZ, format
+  `YYYY,MM,DD,HH,MM,SS`).
+- **No public results page** (`/su/results` → 404). Final scores are exposed only
+  on the event detail page itself via `eventJsonInfo` JSON
+  (`matchIsComplete`, `resultDescription`). Phase 8 must poll until completion;
+  cannot back-fill from an archive endpoint.
+- **Probe environment:** Windows 10 + curl, geo-routed as Poland (`countryCode: PL`).
+  Customer in Belarus may see slightly different KYC overlays — parser must be
+  defensive (treat missing markets as null, never throw).
+- **Captures saved locally** at `spike/captures/*.html` (gitignored): 7 fixtures
+  for offline parser development in Phase 3.