fix(db2): skip column comment for dropped columns in ALTER

[Aias00]

Related issue

Closes #2078

Summary

DB2SqlBuilder.buildAlterTable appended a COMMENT ON COLUMN whenever the column's comment was non-blank, including for a DELETE-status column. For such a column, buildModifyColumn emits ALTER TABLE ... DROP COLUMN "c", then the code appended COMMENT ON COLUMN "schema"."table"."c" IS '...' for the just-dropped column, producing invalid SQL. Added the && !EditStatusEnum.DELETE.name().equals(tableColumn.getEditStatus()) guard (and the EditStatusEnum import), mirroring Oracle (OracleSqlBuilder.java:184-185) and DM.

Affected surfaces

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

Verification

• Commands and results: mvn -B -q -f chat2db-community-server/pom.xml -pl chat2db-community-plugins/chat2db-community-db2 -am -Dmaven.test.skip=true compile -> BUILD SUCCESS.
• Manual verification: For ADD/MODIFY columns with a comment, the COMMENT clause is still emitted (unchanged). For DROP columns, the COMMENT clause is now skipped, avoiding the invalid statement.
• UI evidence: N/A

Risk and compatibility

• Public API or stored data: N/A — only changes generated ALTER text for DROP columns.
• Database or driver compatibility: DB2 ALTER no longer emits an invalid COMMENT for dropped columns; other paths unchanged.
• Network, privacy, or security: N/A.
• Community / Local / Pro boundary: N/A.
• Backward compatibility: Only fixes invalid SQL; no API change.

Reviewer map

• Start here: DB2SqlBuilder.buildAlterTable — comment condition now StringUtils.isNotBlank(tableColumn.getComment()) && !EditStatusEnum.DELETE.name().equals(tableColumn.getEditStatus()); new EditStatusEnum import.
• Failure condition: ALTER for a DROP column still appends a COMMENT ON COLUMN for the dropped column.
• Rollback or disable path: Revert this single commit.

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 fix, verification, and PR description were produced with Claude Code assistance.

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[openai0229]

Reviewed the final DB2 DROP COLUMN fix at fbf69e0. The change only suppresses COMMENT ON COLUMN for DELETE-status columns, matching the existing Oracle/DM behavior; the previous head passed backend checks and Java CodeQL, and the final synchronized head is running the required validation.