Enforce independent skill trigger handling

[cbusillo]

Summary

• clarify rendered skill guidance so independent mandatory/delegated skill matches do not suppress each other
• record command launch order in the exec harness and assert ordered launch prefixes
• add a multi-skill smoke covering Chronicle plus GitHub planning before ordinary work
• tighten GitHub planning smoke to assert the expected issue-list command shape

Validation

• python3 tools/code-exec-harness/harness.py tools/code-exec-harness/scenarios/skill-trigger-binding-smoke.json --skill-root /Users/cbusillo/Developer/codex-skills --inherit-auth
• python3 tools/code-exec-harness/harness.py tools/code-exec-harness/scenarios/github-plan-smoke.json --skill-root /Users/cbusillo/Developer/codex-skills --inherit-auth
• python3 -m py_compile tools/code-exec-harness/harness.py
• jq empty tools/code-exec-harness/scenarios/skill-trigger-binding-smoke.json tools/code-exec-harness/scenarios/github-plan-smoke.json
• ./build-fast.sh