fix: seven bugs from code audit (routing loop, drag overlap, resource leaks)

[pshenok]

A follow-up audit (two parallel agents over routing, drag/drop, campaign, and resource cleanup) surfaced seven distinct bugs. All verified in-browser before fixing.

1. ALB → SQS routing loop + permanent request leak (most severe)

alb → sqs was the only rule in the connection-validity table whose reverse (sqs → alb) is also valid. SQS's forwarding pushes to ALB (Service.js downstreamTypes = ["alb"]), while ALB has no dedicated case and falls into the generic forwarding branch that pushes to any connection with no backpressure check. So an alb ⇄ sqs pair bounces a request ALB→SQS→ALB→SQS… forever — it's never handed to finishRequest/failRequest/removeRequest, leaking it from STATE.requests, growing the queue unbounded, and charging upkeep for zero throughput. Fix: removed the alb → sqs rule; sqs → alb (the real forwarding direction) stays.

2. Campaign burst callbacks leak across Retry / Next

burstPattern schedules up to burstSize setTimeout spawns spaced 20ms apart. The bail-out guard only checked this.active/ended, but Retry and Next call startCampaignLevel → loadLevel directly (which resets ended = false) without exit(). Stale callbacks from the previous attempt then passed the guard and injected phantom requests into the freshly-loaded level, polluting its scoring before the player even pressed Play. Fix: monotonic session id captured at schedule time; a callback bails if the session changed.

3. Drag-drop onto an occupied tile makes a service unremovable

The drag path never applied the overlap guard createService uses. Dropping node B onto node A's tile left them sharing a position; the raycaster only ever returns the front mesh, so the other service became permanently unselectable/undeletable/un-upgradeable while still charging upkeep. Fix: reject the drop (revert to the drag-start tile) when the target tile is occupied.

4. clearAllServices leaked connection GPU resources

Every other connection-removal path disposes geometry/material; "Clear All" only removed the mesh from the scene. Fix: dispose them too.

5. Held keys never cleared on window blur

A keyup missed during an alt-tab left the key stuck in keysPressed, panning the camera forever. Fix: window blur handler clears all held keys.

6. Dragging the Internet node never moved its ring

if (draggedNode.mesh) — but internetNode.mesh is always set, so the else branch (the only one that also moves the ring) was dead code; the cyan ring stayed frozen at spawn. Fix: branch on node identity.

7. _persistWin could poison best time with NaN

A completed[] entry missing bestTimeSec (hand-edited/future schema) made Math.min(undefined, elapsed) = NaN, permanently displaying "NaNs". Fix: Number.isFinite guard.

Verification

In-browser: alb → sqs now rejected while sqs → alb still connects; clearAllServices runs without error; campaign _session increments on each level load (stale callbacks invalidated); _persistWin returns a finite best time (42.5) and correct max stars from a malformed entry. No new console errors. No build step — served raw as before.