feat(sdk): enforce s3:// URIs for string S3 params + ingestion (EL) docs (#9912)

* feat(pipelines): ingestion (EL) templates + docs

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(pipelines): review nits — draft collision guard, template-mode selection reset, invariant test

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(pipelines): lead the insert menu with ingestion templates

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* refactor(pipelines): ingestion story as docs-only — drop editor template UI

The insert-menu template section mixed two selection grammars in one popover and confused more than it helped. The three E2E-verified example pipelines now live verbatim in docs/pipeline-ingestion.md; the Python bare-string S3 key fix in pipelineTemplates.ts stays.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(sdk): bare string S3 keys in py/ts clients + asset parsers

A plain string passed where an S3Object is expected is now a bare key in the default storage — previously the py client silently degraded it to s3="" (auto-generated key) and both asset parsers canonicalized it without the leading slash, splitting lineage. parseS3Object moves to s3Types.ts so it is unit-testable without the generated services. The pipeline template fix from the earlier commit is superseded (bare strings are the supported spelling again); docs examples flipped to bare keys.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* refactor(sdk): enforce s3:// URIs for string S3Object params

Bare strings now raise/throw with a hint pointing at the s3:///<key> spelling instead of being treated as keys (previous commit) or silently degrading to an empty key (original behavior). One string spelling everywhere: SDK calls, // on annotations, and DuckDB SQL all use s3:///<key>. TS regains the s3://-template-literal type; the asset parsers record no asset for a bare string (the call can only error); templates emit the URI form.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs(pipelines): move ingestion (EL) guide to windmilldocs, keep design constraints

User-facing how-to (engine choice, cursor recipes, schema drift, worked examples) moves to windmilldocs core_concepts/63_pipelines (windmilldocs#1462); the repo keeps only the design constraints future feature work must not break, as a section of ducklake-materialization.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* chore: regenerate system prompts after parse_s3_object docstring change

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(sdk): reject empty-key s3 URIs; align asset parsers with the runtime rule

Addresses CI review: s3:/// and s3://bucket/ now raise (an empty key would fall back to the auto-generated-key path the strict contract exists to prevent); the asset parsers' string branch applies the same valid-URI-with-non-empty-key rule so no R/W edge is recorded for a call that can only error (the generic URI-literal scan still records ambiguous access-None assets, by design); comments rephrased as current constraints per AGENTS.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

python-client/tests/wmill_client_test.py

@@ -124,5 +124,49 @@ SET s3_secret_access_key='80yMndIMcyXwEujxVNINQbf0tBlIzRaLPyM2m1n4';
             wmill.load_s3_file(s3_obj)
 
 
+class TestParseS3Object(unittest.TestCase):
+    """Pure-unit tests for parse_s3_object — no network/env needed."""
+
+    def test_bare_string_raises_with_uri_hint(self):
+        # A bare key is rejected rather than silently uploading under an
+        # auto-generated name; the error points at the s3:/// spelling.
+        with self.assertRaisesRegex(ValueError, "s3:///dir/file.json"):
+            wmill.parse_s3_object("dir/file.json")
+
+    def test_triple_slash_uri_is_default_storage(self):
+        self.assertEqual(
+            wmill.parse_s3_object("s3:///dir/file.json"),
+            S3Object(s3="dir/file.json", storage=None),
+        )
+
+    def test_full_uri_splits_storage_and_key(self):
+        self.assertEqual(
+            wmill.parse_s3_object("s3://bucket/dir/f"),
+            S3Object(s3="dir/f", storage="bucket"),
+        )
+
+    def test_malformed_uri_raises(self):
+        # `s3://x` has no key part — fail loudly instead of silently
+        # misplacing the object.
+        with self.assertRaises(ValueError):
+            wmill.parse_s3_object("s3://broken")
+
+    def test_empty_key_uri_raises(self):
+        # An empty key is never a valid target: it would fall back to an
+        # auto-generated key, which is requested by omitting the object.
+        with self.assertRaises(ValueError):
+            wmill.parse_s3_object("s3:///")
+        with self.assertRaises(ValueError):
+            wmill.parse_s3_object("s3://bucket/")
+
+    def test_empty_string_raises(self):
+        # Auto-generated keys are requested by omitting the object (None),
+        # not by an empty string.
+        with self.assertRaises(ValueError):
+            wmill.parse_s3_object("")
+
+    def test_s3object_passes_through(self):
+        self.assertEqual(wmill.parse_s3_object(S3Object(s3="x")), S3Object(s3="x"))
+
 if __name__ == "__main__":
     unittest.main()