#18546: fix(doctor): replace deprecated `auth add` command reference

## Summary Fixes #18535 `openclaw doctor` suggests running `openclaw auth add --provider openai` when no embedding provider is configured for memory search, but the `auth add` subcommand has been deprecated. Replaces both occurrences in `doctor-memory-search.ts` with `openclaw configure`, which is the current command used consistently across the rest of the doctor diagnostics (see `doctor-auth.ts`). ## Test plan - [x] `pnpm vitest run src/commands/doctor-memory-search.test.ts` — 4/4 pass - [x] Lint clean <!-- greptile_comment --> <h3>Greptile Summary</h3> Replaces two references to the deprecated `openclaw auth add` command with `openclaw configure` in the `doctor-memory-search.ts` diagnostic output. This aligns memory-search doctor messages with the convention already used by `doctor-auth.ts`, `doctor-security.ts`, `doctor.ts`, and other doctor diagnostics throughout the codebase. No behavioral or logic changes — purely a user-facing message fix. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge — it only updates two user-facing diagnostic strings with no logic changes. - The change is minimal (two string literal replacements), introduces no new logic, and aligns with the established pattern across all other doctor diagnostics. Tests pass and no other code paths are affected. - No files require special attention. _{Last reviewed commit: 84b7f3c} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->