fix(result): search custom-rendered column names

[openai0229]

Related issue

Closes #2850

Summary

Restore result-set searches for visible custom-rendered column names. The search matcher resolves header text from the stable column metadata while preserving the existing raw cell-value matching behavior.

Affected surfaces

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

Verification

• Commands and results:
  • yarn test:result-set-ui: passed, 36 tests
  • focused ESLint for the three changed files: passed with zero warnings
  • yarn run build:web:community --app_version=0.0.0: passed, including the Community prebuild regression suite and production bundle verification
  • Community Maven package: BUILD SUCCESS with tests explicitly skipped for the runtime build
• Manual verification:
  • Executed a MySQL query returning record_primary_key and customer_business_requirement_description.
  • Searching record_primary matched the visible header and reported item 1 of 1.
  • Searching customer-001 matched the cell value and reported item 1 of 1.
• UI evidence: Playwright CLI verified both result counts and captured the highlighted header state locally.

Risk and compatibility

• Public API or stored data: N/A; no API or persistence changes.
• Database or driver compatibility: N/A; matching uses existing result metadata for every database.
• Network, privacy, or security: N/A; search remains local to the rendered result table.
• Community / Local / Pro boundary: The change stays in the shared result-grid frontend and adds no commercial behavior.
• Backward compatibility: Existing case-sensitive cell-value matching is preserved.

Reviewer map

• Start here: chat2db-community-client/src/blocks/SearchResult/components/FESearch/searchMatcher.ts
• Failure condition: A visible custom-rendered header is not matched, or ordinary cell-value search stops matching.
• Rollback or disable path: Revert commit 1f9ed56 to restore the previous search callback.

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.