feat(ownership): discover above-1% XLSX on the IDX data page

IDX stopped posting the monthly above-1% list as an announcement after
the 2026-05-29 report; June/July/August are only on the Data
Kepemilikan Saham page. `ownership discover` could not see them, and
IDX's Cloudflare now rejects curl_chrome142 on that page and on the
/Media/ XLSX files.

- remote: parse the page's Nuxt payload (Description/Prospectus pairs,
  / escapes), classify above-1% XLSX as supported and above-5% /
  investor-type workbooks as unsupported, derive as_of_date from the
  Indonesian description. Keep all above-1% entries, only the newest
  of the other series. Merge with the announcement results.
- discover JSON gains `format` (xlsx|pdf) and `as_of_date`; page
  entries use the as-of date as publish_date (the page shows none).
- import --url accepts .xlsx and downloads via the XLSX validator.
- curl_impersonate: run_owned_with_fallback tries several browser
  profiles until the body validates (JSON / page payload / %PDF / PK);
  IDX_CURL_IMPERSONATE_BIN still pins one.
- Tests: page fixture parsing, date parsing, payload validation, CLI
  discover via a local page server; existing discover tests now point
  IDX_OWNERSHIP_DATA_PAGE_URL at a closed port so no test hits IDX.
- Docs: ARCHITECTURE discovery section, AGENTS ownership inputs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017a5Cv5Z1NzdYKgKnTiAF4E

docs/ARCHITECTURE.md

@@ -67,6 +67,22 @@ Unlike the `stocks` module (live-fetch), ownership is **import-then-query**:
 - **KSEI archive** — monthly ZIP/TXT balance-position matrix, used as a local fallback/backstop import path
 - **Bing Finance** — global institutional ownership (REST API, quarterly)
 
+### Discovery
+`idx ownership discover` merges two IDX sources:
+- the announcement API (`GetAllAnnouncement`) for the legacy PDF announcements
+- the Data Kepemilikan Saham page (`/id/perusahaan-tercatat/data-kepemilikan-saham/`),
+  whose server-rendered Nuxt payload lists every XLSX with a description such as
+  `Pemegang Saham di Atas 1% per 31 Agustus 2026`; the as-of date comes from that text
+
+Only the above-1% XLSX is `supported`; the daily above-5% and investor-type workbooks
+are listed as `unsupported`. Both URLs can be overridden for tests with
+`IDX_OWNERSHIP_ANNOUNCEMENT_API_URL` and `IDX_OWNERSHIP_DATA_PAGE_URL`.
+
+IDX sits behind Cloudflare, which accepts some curl-impersonate TLS profiles and
+rejects others per path (for example `curl_chrome142` gets 403 on the data page).
+IDX fetches therefore try several profiles until the response validates (JSON, page
+payload, `%PDF`, or `PK` zip magic). `IDX_CURL_IMPERSONATE_BIN` pins a single profile.
+
 ### Parser Pipeline
 ```
 KSEI XLSX → zip + quick-xml (sharedStrings + sheet1) → exact 12-column header check