test(react-router): Fix getMetaTagTransformer tests for Vitest compatibility

[s1gr1d]

• Migrated from Jest done callback to Promise-based async test pattern
• Fixed test assertion by adding missing </head> tag to trigger getTraceMetaTags call (the test did not work before as getTraceMetaTags is only called when there is a closing head tag
• Corrected stream piping logic to properly test transformer functionality
  The getMetaTagTransformer function internally pipes the transformer TO the bodyStream (htmlMetaTagTransformer.pipe(body)). So the correct flow is:
  1. Write data to the transformer
  2. Transformer processes it and pipes to bodyStream
  3. Read the output from bodyStream

[cursor]

Bug: Test Logic Mismatch: Head Tag Presence Affects Meta Injection

The test "should not modify chunks without head closing tag" has inconsistent logic. It provides HTML with a </head> tag and expects meta tag injection, which contradicts its name and the behavior it's meant to verify (no modification when </head> is absent). This leaves the 'no </head> tag' scenario untested.

 

[cursor]

Bug: Test Mismatch: Head Tag Presence vs. Meta Injection

The test "should not modify chunks without head closing tag" now uses HTML input containing a head tag and expects meta tag injection. This contradicts the test name and leaves the scenario of HTML without a head closing tag untested.