AI Client: pass event dispatcher to Prompt Builder

[soderlind]

This patch fixes AI Client event dispatching so lifecycle actions fire as intended.

What was fixed

• The helper function now passes the configured global event dispatcher into the prompt builder.
• The WordPress prompt builder now accepts an optional event dispatcher and forwards it to the underlying SDK prompt builder.
• Constructor fallback behavior was updated so the dispatcher is still preserved if prompt parsing throws and the fallback builder instance is created.

Files changed

• ai-client.php
• class-wp-ai-client-prompt-builder.php

Tests added

• Added regression test verifying helper-level wiring of dispatcher:
  • wpAiClientPromptBuilder.php
• Added regression test verifying constructor-level forwarding of dispatcher:
  • wpAiClientPromptBuilder.php

Trac ticket: https://core.trac.wordpress.org/ticket/64938

Use of AI Tools

AI assistance: Yes
Tool(s): GitHub Copilot
Model(s): Opus 4.6
Used for: Initial code skeleton and test suggestions; final implementation and tests were reviewed and edited by me.

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[soderlind]

@jeffpaul ^^