Fix template test discovery without node:fs globSync

[GsCommand]

Motivation

• The test runner attempted to import globSync from node:fs, which isn't exported and caused a SyntaxError during CI test discovery.
• The intent is to reliably discover optional template test suites and skip missing suites without touching src/index.ts.

Description

• Replaced glob-style patterns with explicit suite directories and a root base URL for resolution in typescript-sdk/scripts/template-tests.mjs.
• Added a small findTestFiles helper that uses existsSync and readdirSync to check for directory existence and collect files ending with *.test.mjs.
• The script now skips missing or empty suites and invokes node --test with explicit file paths for each discovered suite.

Testing

• Ran npm run typecheck in typescript-sdk, which failed due to pre-existing src/index.ts type errors unrelated to this change. (failed)
• Ran npm run build in typescript-sdk, which failed at the DTS generation stage for the same pre-existing type errors. (failed)
• Ran npm run test:unit in typescript-sdk, which failed because the build step failed first. (failed)
• Ran node scripts/template-tests.mjs directly, which exercised the new discovery logic and ran template tests (7 passed, 2 existing runtime tests failed), demonstrating discovery now works without using globSync. (partial pass)

---

Codex Task