Add goal route hint projection

[huangruiteng]

Summary

• add a compact goal_route_hint_v0 builder for agent-scoped quota should-run payloads
• expose the hint in quota JSON/markdown without mutating shared ## Next Action
• document the advisory/read-only boundary and cover run/wait side-agent cases in work-lane smoke

Validation

• python3 examples/work-lane-contract-smoke.py
• python3 examples/quota-plan-smoke.py
• python3 examples/next-action-projection-contract-smoke.py
• python3 examples/quota-scheduler-hint-compaction-smoke.py
• python3 examples/quota-scheduler-policy-smoke.py
• python3 -m compileall -q loopx
• python3 -m loopx.cli --format json check --scan-path loopx/quota.py --scan-path loopx/policies/goal_route_hint.py --scan-path examples/work-lane-contract-smoke.py --scan-path docs/quota-allocation.md --scan-path docs/status-data-contract.md --scan-path docs/product/core-control-plane/rule-seam-map.md
• git diff --check

Note: loopx check still reports the pre-existing loopx-meta duplicate index rows warning.

[huangruiteng]

No blocking findings from my side.

Product/architecture judgment:

• Motivation: this PR addresses a real multi-agent operator problem: quota should-run --agent-id ... can select an agent-lane action while the durable goal ## Next Action still belongs to the primary goal route. Without a compact synthesis, hosts/agents can confuse a lane-local action with a goal-level mutation.
• Solved or not: the implementation does solve the intended boundary for the tested cases. goal_route_hint_v0 is emitted as read-only advisory data, carries preserves_goal_next_action=true / goal_next_action_mutation=none, and the smokes cover both current-agent runnable and other-agent wait cases.
• User/operator impact: this should make heartbeat/Codex-host output less confusing. Operators can see “current lane should run/wait” without losing the shared durable Next Action or hiding other-agent queues.
• Main risk: medium because this touches quota.py hot-path output and adds another advisory field that agents may over-trust. I sampled the live payload: total quota JSON is still large (~177KB in this local state), but the new goal_route_hint itself is compact and markdown renders only a short summary/current action line. Existing Next Action preservation remains explicit.
• Design judgment: extracting the synthesis into loopx/policies/goal_route_hint.py is the right direction; it is cleaner than adding more branching directly into quota.py. Long-term, this can become part of a broader route/advisory projection module, but this PR keeps the contract bounded and read-only.

Validation I ran locally on PR head e783c250:

• python3 examples/work-lane-contract-smoke.py
• python3 examples/quota-plan-smoke.py
• python3 examples/next-action-projection-contract-smoke.py
• python3 examples/quota-scheduler-hint-compaction-smoke.py && python3 examples/quota-scheduler-policy-smoke.py
• python3 -m compileall -q loopx
• python3 -m loopx.cli --format json check --scan-path loopx/quota.py --scan-path loopx/policies/goal_route_hint.py --scan-path examples/work-lane-contract-smoke.py --scan-path docs/quota-allocation.md --scan-path docs/status-data-contract.md --scan-path docs/product/core-control-plane/rule-seam-map.md
• git diff --check origin/main...HEAD
• extra live sample: python3 -m loopx.cli --format json ... quota should-run --goal-id loopx-meta --agent-id codex-side-bypass, confirming goal_route_hint is advisory/compact and active_state_next_action remains separate.

Note: loopx check only reported the known pre-existing loopx-meta duplicate index rows warning.

Merge decision: approved from side-agent review perspective, but I did not admin-bypass merge because this is quota/status hot-path behavior and still has the normal review-required gate.