Related issue

Closes #1914

Summary

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

• Routes Oracle metadata, DB manager, SQL builder, type/index rendering, and DML value processors through one Oracle identifier/literal contract.
• Preserves conditional quoteIdentifier(...) behavior for completion and lookup while using quoteIdentifierAlways(...) at generated-DDL sites.
• Round-trips embedded double quotes and existing outer quotes without losing identifier text.
• Adds quote-aware validation for Oracle type/default expressions so legal expressions such as functions, casts, sequences, intervals, and nested calls are preserved while unbalanced or multi-statement fragments are rejected.
• Adds focused processor, guard, builder, metadata, and value-serialization coverage.

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-oracle -am clean test -DskipTests=false -Dmaven.test.skip=false -Dsurefire.failIfNoSpecifiedTests=false
  • Result: BUILD SUCCESS across 8 reactor modules; 160 tests passed in tested modules, including Oracle 44/44, SPI 90/90, and tools 26/26.
  • git diff --check origin/main...HEAD: passed.
• Manual verification: Source-level generated-SQL review completed. No live Oracle 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: Oracle identifier case behavior remains conditional for lookup/completion; generated DDL now quotes identifiers consistently. Legal Oracle default/type expressions covered by regression tests.
• Network, privacy, or security: No network or privacy change. Reduces malformed SQL and identifier/literal injection risk in metadata-driven DDL/export paths.
• Community / Local / Pro boundary: Community Oracle plugin only; Local and Pro consume the Community plugin behavior without product-specific code changes.
• Backward compatibility: Existing ordinary identifiers and values retain their emitted form; embedded delimiters and quoted names now round-trip correctly.

Reviewer map

• Start here: OracleIdentifierProcessor, OracleSqlGuards, then OracleSqlBuilder and OracleMetaData.
• Failure condition: Identifier text changes after quote/remove round-trip, legal Oracle defaults/types are rewritten, or generated SQL contains raw metadata identifiers/literals.
• 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, review, and test expansion; all final changes were source-reviewed and verified with the commands above.