Add list_code_quality_findings tool to the code_quality toolset #3560

Describe the feature or problem you’d like to solve

The code_quality toolset has get_code_quality_finding, but an agent can only use it if it already knows a finding number. There's no way to ask "what Code Quality findings does this repository have?", so agents can't find, triage, or pick findings to fix without the user looking up numbers in the UI first.

Proposed solution

Add a read-only list_code_quality_findings tool to the existing code_quality toolset, backed by the public REST endpoint List code quality findings for a repository (GET /repos/{owner}/{repo}/code-quality/findings).

• Inputs: owner, repo, state (open | dismissed, default open), direction (asc | desc), and cursor pagination (perPage, after), the same as list_dependabot_alerts.
• Output: the findings as the REST API returns them, plus pageInfo for the next page. The output pairs with get_code_quality_finding, which takes a finding number.
• Auth: same as get_code_quality_finding (repo scope).
• No feature flag or Insiders gating, and no change to the default toolsets.

The API currently filters only by state, so this tool exposes only that filter.

Example prompts or workflows (for tools/toolsets only)

• "What open code quality findings are there in monalisa/smile?"
• "List the code quality findings in monalisa/smile and group them by rule."
• "Which files in monalisa/smile have the most code quality findings?"
• "Show me the 10 most recent code quality findings in monalisa/smile and fix the first one."
• "Which code quality findings have been dismissed in monalisa/smile?"

Additional context

• Builds on the code_quality toolset and get_code_quality_finding added in Add tool for getting code quality findings #2604.
• About GitHub Code Quality.
• I'm happy to open the PR for this.