Cost ledger: autonomy and the check lane act on the ledger, and the decider log says which number moved it #1387

Follows #1386 (the ledger itself: core/cost_ledger.ts, core/ledger_write.ts).

• The lane: when a pull's checks would wait longer than they run (median lane_wait_s vs wall_s of check entries over the last day), that is a reason to raise checks.concurrency or burst; say it on the board as a need with the two numbers.
• Autonomy: a builder's third rework entry on one pull is a reason to park it (crew/parks.ts).
• Each decision recorded through decideAndRecord carries the ledger numbers in its state, and the log names the one that moved it.

Tests: a decision with the ledger numbers in state; a pull with three agent entries is parked; a lane whose wait exceeds its run raises the need.

Parked by the crew: the run ended without a pull: declined: this issue builds on #1386, and #1386 isn't in the repository. core/cost_ledger.ts and core/ledger_write.ts don't exist on main or on this branch. Nothing in src, test or docs mentions `la

Parked by the crew: the run ended without a pull: declined: nothing has changed since my last run. #1386 is still open and unmerged, and origin/main is still at 308286d0. It has no core/cost_ledger.ts or core/ledger_write.ts, and there is no ledger table

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the run ended without a pull: declined: this issue builds on #1386, and #1386 isn't in the repository. core/cost_ledger.ts and core/ledger_write.ts don't exist on main or on this branch. Nothing in src, test or docs mentions `la
2. the run ended without a pull: declined: nothing has changed since my last run. #1386 is still open and unmerged, and origin/main is still at 308286d0. It has no core/cost_ledger.ts or core/ledger_write.ts, and there is no ledger table

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Deferred by the planner. This follows #1386 and builds on its core/cost_ledger.ts and core/ledger_write.ts, which are not on main. The map had it backwards: #1386 waited on this issue, so a builder was handed it before its foundation existed. Twice. It now waits for #1386, and it sits behind the Later gate (#595) because #1386 serves no pillar yet. Lift both links once #1386 lands and the owner opens it.