typescript-sdk: skip missing optional template test suites

[GsCommand]

Motivation

• The template test runner currently invokes node --test on hardcoded globs and fails CI when optional runtime template tests are absent, which should not block TypeScript SDK CI.
• The goal is to treat runtime/tests/*.test.mjs as optional and only run suites that actually have matching test files.

Description

• Added existsSync/readdirSync and path imports and a repoRoot constant to resolve paths relative to the repository root.
• Implemented hasGlobMatches(pattern) which checks whether the target directory exists and whether the filename glob has at least one match using a simple wildcard-to-regex matcher.
• The script now skips any suite whose glob has no matches and still runs node --test for suites that do exist, preserving non-zero exit propagation for failing suites.
• Updated cwd for the spawned node --test processes to use the resolved repoRoot for consistent execution context.

Testing

• npm run typecheck was executed and failed due to pre-existing TypeScript errors in typescript-sdk/src/index.ts, which are unrelated to this script change.
• npm run build was executed and failed during the DTS step for the same pre-existing TypeScript errors in src/index.ts.
• npm run test:unit was executed and failed because it invokes npm run build, which failed for the same reason.
• node scripts/template-tests.mjs was executed directly and the script ran the available runtime/tests and typescript-sdk/tests suites when present and correctly propagated non-zero exits for failing tests.

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Codex Task