Previously, `/memory show --project` and `/memory show --global` only checked
the first filename from `getCurrentGeminiMdFilename()` (i.e., `QWEN.md`),
ignoring other configured context files like `AGENTS.md`. This caused the
commands to report empty even when `AGENTS.md` existed and was being loaded
by the actual memory loading mechanism (`loadServerHierarchicalMemory`).
Changes:
- Replace `getCurrentGeminiMdFilename()` with `getAllGeminiMdFilenames()` in
memoryCommand.ts
- Add `findAllExistingMemoryFiles()` helper that iterates all configured
filenames and aggregates content from all existing files
- Update both `--project` and `--global` subcommands to display content from
all found memory files
- Add tests for fallback (only AGENTS.md exists) and dual-file scenarios
