examples(issue_resolver): rename shared helper to issue_resolver_common and remove GRANDFATHERED_EXAMPLES

[mashood-memon]

Closes #233

What changed

• Renamed examples/issue_resolver_github_context.py → examples/issue_resolver_common.py to match the *_common.py helper module convention
• Updated import in examples/claude_issue_resolver.py, examples/gemini_issue_resolver.py, and examples/ollama_issue_resolver.py
• Removed GRANDFATHERED_EXAMPLES set and TODO comment from tests/test_registry_docs.py — the existing *_common.py filter already excludes helpers
• Updated skip entry in tests/test_examples_smoke.py to reference the new filename
• Added ### Changed entry to CHANGELOG.md under [Unreleased]

Verification

• pytest tests/test_registry_docs.py — 9 passed
• pytest tests/test_examples_smoke.py — same 5 pre-existing failures (missing optional packages: google, trafilatura, rembg, python-pptx, pillow), no new failures introduced

Notes

• examples/README.md, docs/usage/agent_loops.md, and docs/skills/issue_resolver.md do not reference issue_resolver_github_context.py — no changes needed there

[rosspeili]

Thanks @mashood-memon, this is the cleanest take on #233 so far.

Before merge, please add a one-line note on docs/skills/issue_resolver.md that the three *_issue_resolver.py scripts share examples/issue_resolver_common.py, plus a docs-only Skill history row (same bar as #274 review). No manifest bump needed.

Once that’s in and CI is green, good to merge, and I will change the assignee on the issue <3