feat: add 3 new error entries (runner-environment x2, known-unsolved x1)

[htekdev]

New Error Entries

ID	File	Category	Source
re-493	add-to-project-content-already-exists-in-project.yml	runner-environment	actions/add-to-project#389 (13 reactions)
re-494	first-interaction-v3-issue-message-required.yml	runner-environment	actions/first-interaction#365 (6 reactions)
ku-142	codeql-merge-queue-status-not-reported.yml	known-unsolved	github/codeql-action#1537 (41 reactions)

Summary

• re-493: actions/add-to-project crashes with "Content already exists in this project" GraphQL error when attempting to add an issue/PR already on the board. Fix: restrict trigger to issues: [opened] or use continue-on-error: true.

• re-494: actions/first-interaction v3.1.0 broke issue-message from optional to required in a minor version bump. Workflows that only set pr-message now fail with Input required and not supplied: issue_message. Fix: add issue-message: ''.

• ku-142: CodeQL scans triggered by merge_group events do not post the Code Scanning status check back to the PR, breaking merge queues where CodeQL is a required status check. GitHub platform limitation — no runner-side fix.

Research

Strategy 5 round 253 — GitHub Community Discussions + Issues mining (Exa/Perplexity over quota; GitHub Issues API fallback).