fix: resolve plugin initialization race condition (#75)

[MarcosBrendonDePaula]

Summary

• Moved initializeAutomaticPlugins() from fire-and-forget in the constructor to await inside start(), ensuring all auto-discovered plugins are fully initialized before the server accepts traffic.
• Added 10 unit tests covering lifecycle hook ordering, dependency validation, onConfigLoad execution, and error resilience.

Closes #75

What was the problem?

// constructor — fire-and-forget ❌
this.initializeAutomaticPlugins().catch(error => {
  logger.error('Failed to initialize automatic plugins', { error })
})

If listen() was called before plugin discovery finished, auto-discovered plugins would miss setup(), onBeforeServerStart(), onServerStart(), and onAfterServerStart() hooks.

What changed?

• core/framework/server.ts: Removed fire-and-forget from constructor; added await this.initializeAutomaticPlugins() at the top of start()
• tests/unit/core/plugin-init-race-condition.test.ts: 10 new tests

Test plan

• New test file passes (10/10 tests)
• Full test suite passes (577 passed, 0 failed)
• Manual: bun run dev starts without regressions

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