fix: make paused quota authoritative

[cocolord]

Summary

• allow configure-goal --quota-compute 0 as the supported pause configuration
• make paused quota override workspace repair, capability bridge repair, autonomous replan, monitor, inbox, and fallback execution paths
• project a quiet no-spend interaction and scheduler contract while paused

Validation

• uv run --extra test pytest -q tests/control_plane/test_quota_paused_precedence.py (4 passed)
• adjacent control-plane tests (29 passed)
• uv run loopx canary premerge --from-git-diff (passed, 17 checks; one unrelated inherited maintainability advisory)
• live readback against three paused goals and four registered agents: all returned state=paused, decision=skip, should_run=false, effective_action=quota_skip

Hold

Draft for maintainer review. No goals are resumed or merged by this PR.