Eagerly print test name before execution to expose hanging tests

[Copilot]

The runner printed test names only after completion, making it impossible to identify which test was hanging — the output would simply stop with no indication of what was running.

Changes

• printTestStart(name): Prints name ... (no trailing newline) and flushes stdout before the test runs
  • sys: Sys.print() + Sys.stdout().flush()
  • js: process.stdout.write(...)
  • other targets: trace(...) fallback (separate line)
• printTestEnd(passed, detail): Prints just the status (OK / FAIL: ...) after the test, completing the line
• Removed printResult(name, passed, detail) which did the full print post-execution
• printTestStart is called before the try block so a hang is always visible in output

Output

TestBasic
  testSimple ... OK
  testDelay ...        ← visible immediately; hangs here if test blocks

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