fix(github-issues): ban conventional commit prefixes in issue titles

Issue titles were being created with fix(x):, feat(x):, ref(x): etc.
These formats belong in commit messages and PR titles, not GitHub issues.

Added explicit hard constraint in SKILL.md and anti-pattern in
issue-examples.md to prevent this.

Co-Authored-By: sentry-junior[bot] <264270552+sentry-junior[bot]@users.noreply.github.com>

Author: dcramer

packages/junior-github/skills/github-issues/SKILL.md

@@ -52,6 +52,7 @@ Follow [references/research-rules.md](references/research-rules.md) for cross-ty
 **Hard constraints — apply to every new issue:**
 
 - Title ≤ 60 characters. Descriptive for bugs, imperative for tasks/features.
+- **Issue title format: plain language, no type prefix.** Do not use `fix(x):`, `feat(x):`, `chore:`, `ref(x):`, or any other type-scope prefix — those belong in commit messages and PR titles, not issues.
 - Summary ≤ 3 sentences. Do not restate the title in the body.
 - Prefer flat bullet lists over headed sections for simple issues. Remove empty sections.
 - Generalize session framing — strip channel references, slash commands, Slack thread IDs, user @mentions, and transcript fragments; replace with the underlying technical problem.