Test: release Go-proxy RESTful contract tests verified passing in Go mode (#17468)

### Summary

Aligns Go and Python error codes/messages so both backends honor the
same RESTful API contract, removing implementation-specific error leaks
(MySQL errors, `ValueError`, `AttributeError`, Gin validator format) in
favor of clean business error codes.

**Chat list** — invalid `orderby` now returns code 101 (was: raw Python
`AttributeError` code 100); invalid `page`/`page_size` values fall back
to defaults (was: raw `ValueError`/`ProgrammingError` code 100).

**Dataset create/update/delete** — adds UUID validation (101),
extra-field rejection (101), duplicate-id detection (101), content-type
/ JSON-syntax / object-shape checks (101), and "lacks permission" for
nonexistent datasets (IDOR). Create auto-deduplicates dataset names.
Pagerank updates tolerate a missing ES index. List response includes
`parser_config` and `pagerank`.

**Session list/update** — adds filtering, sorting, and pagination
support. Empty payloads are valid no-ops. Authorization errors map to
code 109.

**Chunk list** — doc object uses Python key names (`chunk_count`,
`dataset_id`, `chunk_method`, run text status). Add validates list
element types.

**Document update** — adds `chunk_method` alias, pydantic-style Field
error messages, metadata index auto-create with refresh, and "These
documents do not belong to dataset" messages. List validates
`metadata_condition` and reports ownership errors for unmatched name/id
filters.

**Search completion** — `kb_ids` ownership failure returns code 102
instead of 109.

Released 31 contract tests from `GO_ONLY_SKIPS` (all verified passing on
both Go and Python backends with real LLM keys).

internal/entity/dataset.go

@@ -224,16 +224,18 @@ type KnowledgebaseDetail struct {
 // KnowledgebaseListItem represents a knowledge base item in list responses
 type KnowledgebaseListItem struct {
 	ID           string  `json:"id"`
-	Avatar       *string `json:"avatar,omitempty"`
+	Avatar       *string `json:"avatar"`
 	Name         string  `json:"name"`
-	Language     *string `json:"language,omitempty"`
-	Description  *string `json:"description,omitempty"`
+	Language     *string `json:"language"`
+	Description  *string `json:"description"`
 	TenantID     string  `json:"tenant_id"`
 	Permission   string  `json:"permission"`
 	DocNum       int64   `json:"doc_num"`
 	TokenNum     int64   `json:"token_num"`
 	ChunkNum     int64   `json:"chunk_num"`
 	ParserID     string  `json:"parser_id"`
+	ParserConfig JSONMap `json:"parser_config"`
+	Pagerank     int64   `json:"pagerank"`
 	EmbdID       string  `json:"embd_id"`
 	TenantEmbdID *string `json:"tenant_embd_id,omitempty"`
 	Nickname     string  `json:"nickname"`