feat(content-extractor): add support for pull_request triggers

[avivkeller]

As titled. Adds support for pull request related triggers. While this can't see PR content, it can still moderate for AI-like PR bodies

[Copilot]

Pull request overview

Adds support for pull_request and pull_request_target webhook events so the action can extract and evaluate PR title/body content when a PR is opened.

Changes:

• Extend extractFromEvent to extract content/number from pull_request and pull_request_target opened events.
• Update shouldProcess to allow processing of PR opened events for those triggers.

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[Copilot]

In this new pull_request/pull_request_target branch, interpolating optional title/body into a template literal will stringify null/undefined (e.g., "...\nnull"), which can pollute moderation input and potentially cause false positives. Consider normalizing with ?? '' (and optionally trimming) so missing fields don't become the literal strings "null"/"undefined".

Suggested change

	content = `${context.payload.issue?.title}\n${context.payload.issue?.body}`
	issueNumber = context.payload.issue?.number ?? null
	} else if (
	(event === 'pull_request' || event === 'pull_request_target') &&
	context.payload.action === 'opened'
	) {
	content = `${context.payload.pull_request?.title}\n${context.payload.pull_request?.body}`
	const title = context.payload.issue?.title ?? ''
	const body = context.payload.issue?.body ?? ''
	content = `${title}\n${body}`.trim()
	issueNumber = context.payload.issue?.number ?? null
	} else if (
	(event === 'pull_request' || event === 'pull_request_target') &&
	context.payload.action === 'opened'
	) {
	const title = context.payload.pull_request?.title ?? ''
	const body = context.payload.pull_request?.body ?? ''
	content = `${title}\n${body}`.trim()

[Copilot]

New support for pull_request / pull_request_target events is added here, but there are existing Jest tests for extractFromEvent/shouldProcess and none cover these new event types. Please add tests for both events with action opened (including title/body extraction) to prevent regressions.