fix(kingbase): list procedures from the plugin instead of the jdbc driver

[openai0229]

Related issue

No linked issue. The failure was reported directly from the desktop client's error payload
against a KingbaseES datasource (GET /api/rdb/procedure/list); searching the tracker for
kingbase, procedure, and operator does not exist found no existing report for it.

Summary

Opening the procedure list of a KingbaseES datasource failed with:

com.kingbase8.util.KSQLException: ERROR: operator does not exist: boolean || oid
  Position: 173
    at com.kingbase8.jdbc.KbDatabaseMetaData.getProcedures(KbDatabaseMetaData.java:1094)
    at ai.chat2db.spi.DefaultSQLExecutor.procedures(DefaultSQLExecutor.java:620)
    at ai.chat2db.spi.DefaultMetaService.procedures(DefaultMetaService.java:178)

KingBaseMetaData overrides functions() and the single procedure(), but never the
list-level procedures(), so the call fell through DefaultMetaService.procedures to
DefaultSQLExecutor.procedures, which asks the JDBC driver. The driver builds SPECIFIC_NAME
as p.proname || '_' || p.oid AS SPECIFIC_NAME; the reported Position: 173 lands on the
second ||, whose right operand is p.oid.

On a server running in MySQL compatibility mode || is a logical OR, so p.proname || '_'
is typed boolean and the second operator has no overload — exactly the reported
boolean || oid. Some driver builds detect that mode and switch to concat(p.proname,'_',p.oid);
the drivers this plugin ships, kingbase8-8.6.0.jar (default) and kingbase8-8.2.0.jar, have
no such branch, so the driver statement is sent as is. It is assembled inside the driver, so
the plugin layer is the only place to fix it — as the other PostgreSQL-family plugins (xugudb,
sundb, oscar) already do.

The plugin now lists procedures from sys_catalog.sys_proc the way its existing
FUNCTION_LIST_SQL lists functions: joined to sys_namespace, schema bound, extension-owned
objects excluded. Procedures are selected with prokind = 'p' OR (prokind = 'u' AND prorettype = 2278): V8R6 and later mark them 'p', while V8R3 tags every user routine 'u'
and distinguishes a procedure only by its void return type (2278 is void, a function returning
int is 23). Rows map to Procedure with the name trimmed and blank names dropped, keeping the
filtering the previous DefaultMetaService implementation applied.

Affected surfaces

• Frontend / Web
• Backend / API / Storage
• Database plugin / Driver
• JCEF / Desktop packaging
• CI / Build / Release
• Documentation only

Verification

• Reproduced against a real KingbaseES V009R003C018 server in MySQL compatibility mode with
  the plugin's default driver kingbase8-8.6.0.jar: DatabaseMetaData#getProcedures throws
  com.kingbase8.util.KSQLException: ERROR: operator does not exist: boolean || oid, first frame
  com.kingbase8.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2679) —
  same class and same frame as the report.
• The patched KingBaseMetaData#procedures then ran through the same connection and driver on
  that server and returned the schema's procedures instead of failing.
• Checked again on KingbaseES V008R003C002B0290 (V8R3, driver kingbase8-8.2.0.jar, the only
  shipped driver that accepts that server): the plugin path returns the procedures and excludes a
  function of the same schema, while the driver path additionally lists that function as a
  procedure.
• Module test set: mvn -B -f chat2db-community-server/pom.xml -pl :chat2db-community-kingbase -am -Dmaven.test.skip=false -DskipTests=false '-Dsurefire.includes=**/*Test.java' -Dmaven.test.failure.ignore=false test
  → BUILD SUCCESS, 0 failures (spi 191, postgresql 70, kingbase 28 including the new test).
• mvn -B -f chat2db-community-server/pom.xml -pl :chat2db-community-kingbase -am -Dmaven.test.skip=true package → BUILD SUCCESS.
• KingBaseProcedureListTest drives procedures() through a proxy connection and asserts the
  prepared statement is PROCEDURE_LIST_SQL, that the SQL carries no ||, that the schema is
  bound, and that names are trimmed and blank rows skipped. The proxy throws
  UnsupportedOperationException for anything but prepareStatement, so the driver path cannot
  return unnoticed.
• Not covered: the reporter's own V8R6 server, and the Oracle/PostgreSQL compatibility modes of
  KingbaseES. The statement is compatibility-mode independent, and the two tested versions cover
  both prokind conventions.
• UI evidence: N/A

Risk and compatibility

• Public API or stored data: none. Same endpoint, same response model.
• Database or driver compatibility: Kingbase plugin only; the JDBC driver is no longer used for
  this call. The sys_catalog names and the prokind/prorettype markers were checked on V8R3
  and V9R3.
• Network, privacy, or security: none.
• Community / Local / Pro boundary: community plugin only.
• Backward compatibility: when schemaName is blank the new query returns an empty list, where
  the driver path returned search-path-visible procedures. Callers (schema tree, completion)
  pass a schema for Kingbase, and the plugin's functions() already behaves this way.

Reviewer map

• Start here: chat2db-community-kingbase/src/main/java/ai/chat2db/plugin/kingbase/KingBaseMetaData.java (procedures) and .../constant/SqlConstant.java (PROCEDURE_LIST_SQL).
• Failure condition: if the procedures() override is removed, the driver statement comes back and KingbaseES fails again with operator does not exist: boolean || oid.
• Rollback or disable path: revert the two commits; the endpoint returns to the driver-based behaviour.

Contributor declaration

• I linked the Issue that defines this change.
• I tested the affected behavior and reported the actual results above.
• I did not include credentials, private data, or generated build output.
• I disclosed substantial AI assistance below, or this PR contains no substantial AI-generated code.

AI assistance: the change and its test were drafted with an AI coding agent. The failing statement
was traced through the shipped driver bytecode, reproduced and re-checked on real KingbaseES
instances of two versions, and the final diff was reviewed before submission.