feat(ownership): import IDX above-1% XLSX holder register

Since June 2026 IDX publishes the monthly "Pemegang Saham di Atas 1%"
list as an XLSX workbook on the Data Kepemilikan Saham page instead of
a PDF announcement. Add a parser for it and accept `.xlsx` in
`ownership import --file`.

- src/ownership/xlsx.rs: zip + quick-xml reader (shared strings incl.
  rich text, sheet cells), exact 12-column header match so the daily
  above-5% and investor-type/classification workbooks are rejected,
  Excel serial dates, numeric shares, percent -> bps with float-noise
  rounding. Builds KseiHoldingDraft directly and reuses the entity
  normalizers, so investor types stay uppercase like the PDF path.
- Fixtures: trimmed excerpts of the real 2026-08-31 above-1% and
  2026-09-23 above-5% workbooks.
- Unit + CLI tests: import, ticker, releases, above-5% rejection.
- Docs: ARCHITECTURE parser pipeline, AGENTS ownership inputs.

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

src/ownership/entities.rs

@@ -212,7 +212,7 @@ pub fn resolve_entity(
     Ok(entity_id)
 }
 
-fn normalize_investor_type(raw: &str) -> Option<InvestorTypeCode> {
+pub(crate) fn normalize_investor_type(raw: &str) -> Option<InvestorTypeCode> {
     let value = raw.trim();
     if value.is_empty() {
         None
@@ -221,7 +221,7 @@ fn normalize_investor_type(raw: &str) -> Option<InvestorTypeCode> {
     }
 }
 
-fn normalize_locality(raw: &str) -> Option<Locality> {
+pub(crate) fn normalize_locality(raw: &str) -> Option<Locality> {
     match raw.trim().to_uppercase().as_str() {
         "L" | "D" => Some(Locality::Local),
         "F" | "A" => Some(Locality::Foreign),