fix(ci): grant issues:write to welcome workflow for fork PR comments

[cobusgreyling]

The welcome-contributors workflow posts comments via the Issues API. Fork PR runs were failing with 403 because only pull-requests: write was declared — issues: write is also required.

Unblocks welcome checks on contributor PRs like #141.

[github-actions]

Loop Readiness Audit

Score: 100/100 (L3)

Strong loop readiness — good candidate for L3 with explicit gates.

Top suggestions

• Create loop-constraints.md with denylist paths, push/merge rules, and human gates (see templates/loop-constraints.md)

_{Posted by audit.yml · loop-audit docs}