Related issue

Closes #1914

Summary

Completes the KingBase database-plugin portion of the identifier and literal escaping work.

• Aligns KingBase identifier processing with the PostgreSQL-derived conditional quoting, reserved-word, case, and always-quote round-trip contracts.
• Uses unconditional identifier quoting across metadata, DDL, manager, inherited select/count/insert/update/drop, and template paths.
• Preserves schema qualification, case-only renames, custom type expressions, partition names, and definition casing.
• Reuses the PostgreSQL structural validation baseline for nested defaults and user-defined or parameterized type expressions while rejecting comments, statement boundaries, unbalanced input, and appended column clauses.
• Quotes index, constraint, table, schema, column, update, and primary-key names consistently and serializes charset text as an escaped string literal.
• Expands regression coverage for generated SQL and adversarial metadata names.

Affected surfaces

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

Verification

• Commands and results:
  • mvn -B -f chat2db-community-server/pom.xml -pl chat2db-community-plugins/chat2db-community-kingbase -am clean test -DskipTests=false -Dmaven.test.skip=false -Dsurefire.failIfNoSpecifiedTests=false
  • Result: BUILD SUCCESS across 9 reactor modules; 184 tests passed in tested modules, including KingBase 19/19, PostgreSQL 49/49, SPI 90/90, and tools 26/26.
  • git diff --check origin/main...HEAD: passed.
• Manual verification: Source-level generated-SQL review completed. No live KingBase instance was used.
• UI evidence: N/A

Risk and compatibility

• Public API or stored data: No public API or stored-data schema change. Uses the existing shared ISQLIdentifierProcessor contract.
• Database or driver compatibility: Conditional lookup/completion quoting remains PostgreSQL-compatible; metadata-driven generated SQL always quotes raw names. Legal nested defaults and custom or parameterized types are covered by regression tests.
• Network, privacy, or security: No network or privacy change. Reduces malformed SQL and identifier/literal injection risk in generated metadata, DDL, export, and DML paths.
• Community / Local / Pro boundary: Community KingBase plugin only; Local and Pro consume the Community plugin behavior without product-specific code changes.
• Backward compatibility: Ordinary identifiers, defaults, types, and values retain their emitted form; mixed-case names, embedded delimiters, and case-only renames now preserve object identity.

Reviewer map

• Start here: KingBaseSQLIdentifierProcessor, KingBaseSqlGuards, then KingBaseSqlBuilder, KingBaseMetaData, and KingBaseDBManager.
• Failure condition: Quote/remove loses raw text, legal defaults/types are rewritten, generated SQL contains raw metadata identifiers, schema qualification is lost, or custom types/partitions are silently changed.
• Rollback or disable path: Revert this PR; no migration or persisted-data rollback is required.

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: Substantial AI-assisted maintainer revision, multi-agent review, and test expansion; all final changes were source-reviewed and verified with the commands above.