Worker scheduling invariants ("one agent at a time", "one exclusive
workspace lock at a time") were enforced across three parallel
structures: `activeByAgent: Map<string, string>`,
`activeByWorkspace: Map<string, string>`, and `queue: RunJob[]`. Every
claim, release, and tick had to update them in lockstep, with defensive
comments explaining the ordering to future readers.
Replace with one `active: Map<runId, ActiveRun>` where ActiveRun
carries agentId + workspaceKey. Busy checks iterate the map (≤ dozens
of entries); dispatch is a single set + splice. Release is a single
delete. No parallel structures to keep in sync.
- Add `isAgentBusy(agentId)` and `isWorkspaceBusy(lockKey)` as local
helpers — both O(n) over the active map, which is fine at this scale.
- `tickQueue` is claim-before-dispatch: writes `active.set` synchronously
before `startRun` so no async window exists between claim and
dispatch.
- Drop the `lockKey` parameter threading through `startRun` — the map
carries it.
ZacharyZhang-NY
ecd1bc2e33