Recognize contributor-wanted readiness

[laclance]

Summary

Fix a false-negative seen in private production run #13 for Traefik issues such as:

• traefik/traefik#13999

That issue carries both:

• kind/bug/possible
• contributor/wanted

The scanner currently treats kind/bug/possible as a pending-triage dialect but does not recognize contributor/wanted as the corresponding project-owned contributor-ready signal, so it rejects the issue as awaiting maintainer triage.

This change adds contributor/wanted to the shared contributor-ready label dialects.

Safety boundary

• plain kind/bug/possible remains pending triage
• contributor/wanted only clears the generic triage gate
• specific readiness holds such as reproduction, design, investigation, clarification, or discussion still apply through the existing readiness policy
• no competition, scoring threshold, or source behavior changes

Regression coverage

• shared readiness signal recognizes contributor/wanted
• full strategic rejection accepts kind/bug/possible + contributor/wanted past generic triage
• zero-comment preflight behaves the same
• plain kind/bug/possible remains covered as pending triage

Scope

Only:

• opportunity_scout/scoring.py
• tests/test_scoring.py
• tests/test_app.py

No private-instance or release changes.