[codex] refactor: retire weekly ci layer

[xiaojiou176]

Summary

• retire weekly as a first-class CortexPilot CI/profile/workflow layer and keep only pre-commit, pre-push, hosted, nightly, and manual
• move repo-owned weekly command/profile/env/script surfaces onto nightly or manual, including the UI ops command, CI policy profile/schema, env registry, and helper aliases
• rename the continuous-governance weekly target chain to nightly ramp, rename the changed-scope scheduled workflow/script labels, and sync README/docs/AGENTS wording to the 5-layer contract

Test Plan

• bash scripts/test_ci_policy_resolution.sh
• git diff --check
• python3 scripts/check_ui_matrix_p2_nightly_ramp.py --help
• python3 scripts/ui_regression_trend_append.py --help
• bash scripts/ui_regression_operational_gate.sh --help
• bash scripts/run_continuous_governance_ops.sh --help
• python3 scripts/report_changed_scope_quality.py --input-jsonl tests/fixtures/changed_scope/changed-scope-feedback.sample.jsonl --output-dir .runtime-cache/test_output/changed_scope_quality_codex_smoke --base-config configs/changed_scope/rule_tuning.json
• python3 scripts/check_ui_matrix_p2_nightly_ramp.py --tiers P2 --surfaces dashboard,desktop --target-partial-max 56 --target-covered-min 7 --baseline-week-start 2026-02-27 --baseline-partial 63 --baseline-covered 0 --min-gap-reduction 1.0 --min-scoped 0 --fail-closed-mode off --report-out .runtime-cache/test_output/ci/codex_nightly_ramp_smoke.json

Breaking Changes

None

Rollout / Risk

• Risk level: Medium
• Why: touches .github/, CI governance scripts, schema/config, and root docs, but stays within the existing 5-layer contract direction and removes aliases rather than adding new paths
• Rollback: revert commit 877400c

Checklist

• Self-reviewed code
• No debug/print statements left
• No TODO without issue reference
• Documentation updated
• Tests added/updated where the contract surface changed