Panic (nil pointer) on EXEC with @@json for methods with schema-less response columns #726

Summary

EXEC <resource>.<method> @@json = '...' panics with a nil pointer dereference during plan building for methods whose response tabulation yields a column with no resolved schema. No HTTP call is made; the process crashes.

Root cause parent: stackql/any-sdk#130 (newWrappedSchemaFromAnySdkSchema wraps a nil inner schema, producing a non-nil wrapper that defeats nil checks).

Observed with stackql v0.10.605, clickhouse provider v26.08.00442.

Repro

EXEC clickhouse.services.services.update_password
  @serviceId = '<uuid>'
  @@json = '{"newPasswordHash": "x", "newDoubleSha1Hash": "y"}';

panic: runtime error: invalid memory address or nil pointer dereference
github.com/stackql/any-sdk/public/formulation.(*wrappedSchema).GetType(...)
	wrappers.go:1378
github.com/stackql/stackql/internal/stackql/drm.(*staticDRMConfig).GenerateSelectDML(...)
	internal/stackql/drm/drm_cfg.go:725
github.com/stackql/stackql/internal/stackql/primitivegenerator.(*standardPrimitiveGenerator).assembleUnarySelectionBuilder(...)
	unary_selection.go:118
... AnalyzeUnaryExec -> analyzeExec -> AnalyzeStatement -> handleExec

Analysis

GenerateSelectDML guards with if col.GetSchema() != nil, but the value returned is a non-nil *formulation.wrappedSchema wrapping a nil anysdk.Schema, so the guard passes and GetType() dereferences nil (drm_cfg.go:723-725).

The method's 200 response is a plain object (status, requestId, result with one string property); one of the tabulated columns resolves no schema.

Suggested resolution

• Primary: fix the wrapper factory in any-sdk (parent issue) so nil stays nil.
• Defensive: drm_cfg.go already has an else-branch for schema-less columns (falls back on col.GetVal()); with the wrapper fixed, that branch would be taken instead of panicking. Optionally harden the guard to tolerate typed-nil wrappers.
• A plan-builder panic should be recoverable per statement rather than crashing the process (affects server mode too).