test(ingest): SQL connector + load-bearing + golden, detach-proven (I4)

New: test_ingest_sql.py (connector mechanics + typed rendering + dispatch), test_ingest_sql_loadbearing.py (SQL seams: typed-NULL, typed-REAL, navigability via unchanged okf), test_ingest_golden_sql.py + examples/ingest-golden-sql/ (byte-frozen sqlite golden; NULL->empty, 4200.0->4200.0 and escape discriminate a typed impl from naive ones). Updated: sql-source refusal test repointed to http (I6); manifest schema-breadth comment. Each new seam proven RED at its detach point.

Refs: shared/ingest-spec.md 11 golden + load-bearing table

examples/ingest-golden-sql/expected-bundle/index.md

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+Golden extraction case: two SQL extracts from a local project database (sql source type).
+- [Project costs](ingest-costs.md)
+- [Catalogue metadata](ingest-meta.md)

examples/ingest-golden-sql/expected-bundle/ingest-costs.md

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+---
+type: dataset
+title: Project costs
+source_system: portefolje-db
+source_query: SELECT id, item, amount, note FROM costs ORDER BY id
+ingested_at: 2026-07-04T12:00:00Z
+ingest_manifest: manifest@a4b891aea55df97b
+generated: true
+---
+
+| id | item | amount | note |
+| --- | --- | --- | --- |
+| 1 | LED-armatur | 1200.5 | godkjent |
+| 2 | sensor | 89.9 |  |
+| 3 | kabel | 4200.0 | rest |

examples/ingest-golden-sql/expected-bundle/ingest-meta.md

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+---
+type: reference
+title: Catalogue metadata
+source_system: portefolje-db
+source_query: SELECT k, v FROM meta ORDER BY k
+ingested_at: 2026-07-04T12:00:00Z
+ingest_manifest: manifest@a4b891aea55df97b
+generated: true
+---
+
+| k | v |
+| --- | --- |
+| owner | anlegg \| drift |
+| path | c:\\temp |