Export dc-auto-top leg liveness and DCA input gauges

[madninja]

Why

A dc-auto-top leg is self-rescheduling: each run queues its own next task as its last step. A healthy leg therefore always points at a task whose trigger is in the future.

Every way a leg breaks ends the same way, with no reschedule: a stale or wrong-owner price oracle, an empty DCA input account, a leftover dca PDA from an undrained run, lamports below the rent-exempt plus crank-reward floor, or a reverting swap. tuktuk then retries the task until it goes stale, sweeps it, and nothing restarts the leg without schedule_task_v0.

Nothing observed that. The carrier offload leg's HNT half sat broken for several days and the only alert that would eventually have noticed is a balance threshold that trips ~2 days later, once the HNT buffer has drained.

What

solana_auto_top_off_task_trigger{name,leg} reports the trigger time of the task each leg currently points at, and 0 when none is scheduled. One expression covers both failure shapes:

time() - solana_auto_top_off_task_trigger{leg="hnt"} > 3600

A healthy leg has a future trigger so the difference is negative; a leg that is failing to execute has a past one; and 0 makes the same expression catch a swept task rather than needing a second clause.

Also exported, since they are the two inputs the HNT leg's DCA reads and neither was visible:

• auto-top-off USDC balances (solana_account_balance{type="usdc"}). The DCA transfers a whole run's worth up front, so a shortfall reverts the run rather than shrinking it, which is the no-reschedule path above.
• USDC/USD pyth publish time (solana_pyth_publish_time{name="usdc"}). The leg refuses to start on a feed older than five minutes. Only the HNT feed was exported.

This finally uses the USDC_MINT constant that has been declared and unreferenced in index.ts.

Notes for review

• helium_mobile_auto_topoff/hnt reports 0, permanently. Helium Mobile is decommissioned as a separate payer: its traffic moved onto the normal carrier offload router (112c85vb…), which is why that router now carries the helium_mobile volume while the custom router 112Kdmt… is a rump. So Bvge1…'s HNT leg is not going to be revived, and its 0 is correct rather than a defect. An alert on leg="hnt" must scope to name="carrier_auto_topoff"; leg="dc" is still meaningful for both, since that account's DC leg is live. Flagging so the rule is not written against a permanently-firing series.
• An RPC failure deliberately does not zero the gauge. The handler logs and leaves the previous reading, because reporting a transient read failure as a stalled leg would page on every blip; watch retries every 5 minutes. The tradeoff is that a persistent partial failure holds a stale healthy-looking value, which is the same property solana_pyth_publish_time already has.
• The lockfile diff includes unrelated churn. Adding the two dependencies re-resolved ws@8.18.0 to 8.18.2 inside the @orpc/* peer-suffix strings. Any fresh pnpm install produces this, and hand-editing a lockfile to avoid it would be worse.

Verification

pnpm turbo run build --filter=@helium/monitor-service is green, run against a tree using the same pre-built idls plus target/types placeholder the Dockerfile itself sets up, which is what CI's test-docker-builds gate exercises.

The compiled monitors were also run against mainnet and their emitted metrics read back, rather than relying on the build alone:

solana_auto_top_off_task_trigger{name="carrier_auto_topoff",leg="dc"}          1787068800   (16:00Z, healthy)
solana_auto_top_off_task_trigger{name="carrier_auto_topoff",leg="hnt"}         1787069100   (16:05Z, healthy)
solana_auto_top_off_task_trigger{name="helium_mobile_auto_topoff",leg="dc"}    1787068800   (healthy)
solana_auto_top_off_task_trigger{name="helium_mobile_auto_topoff",leg="hnt"}            0   (no task)
solana_pyth_publish_time{name="usdc"}                                         1787000639
solana_account_balance{name="carrier_auto_topoff",type="usdc"}                         0

The timestamp decode path is exercised by those non-zero readings, so the now-trigger fallback is the only unexercised branch.