Cost UX round 2: live ticking, breakdown toggle fix, /cost page, clear confirm

[aakri0]

Five things you flagged, all fixed.

1. Live cost while running

actual_cost() now also handles status=running — it adds (now - started_at) onto the prior cumulative duration and tags the result live: true. The UI polls /jobs/{id} at 500ms while running, renders a pulsing LIVE pill next to the actual cost, and the number visibly ticks up in the strip.

Verified end-to-end: a 3s time.sleep(3) job ticks $0.0000139 → $0.0000271 → $0.0000403, then locks in at $0.0000404 (live=false) when it completes.

2. Breakdown toggle was broken

The CSS .cost-strip-detail { display: flex } overrode the UA stylesheet's [hidden] { display: none }, so the row was always visible regardless of the toggle. Added explicit [hidden] rule and the click-to-expand on the Actual cell now works.

3. "Estimated max" label clarified

The strip label now reads:

Estimated max (worst-case upper bound — assumes every retry hits its full timeout)

So the meaning is visible without hovering for a tooltip.

4. Clear-invocations confirmation modal

The old confirm() is replaced with a proper modal that previews:

• About to delete: N completed (or whatever filter is active)
• Cost recorded against these: total $ ...
• explicit copy: "Your Last 30 days total and the Cost page breakdown will drop accordingly."

After the delete, both refreshUsageTotal() and refreshCostPage() fire so the cost panels update immediately.

5. New #cost page

A new sidebar tab. Two cards:

• How it's calculated — the formula, the four rate knobs (with current values pulled from /usage/cost.pricing), the inputs the model uses (duration_seconds, vcpu_share, memory_mb, attempts, network_seconds), an explicit definition of Estimated max, and a note about what Clear does.
• Your usage (last 30 days) — total + count headlines, plus a by-status breakdown table (completed, failed_permanently, canceled with their counts and summed cost).

Refreshes when the tab opens and after every Invoke / burst / clear.

Test plan

• pytest -q — 174 passed (3 new pricing cases for live cost, mid-flight retry, missing started_at).
• Live cost ticks visibly on a 3s job.
• Click Actual — breakdown row expands; click again — it collapses.
• Click Clear finished — modal opens with N + cost preview; cancel = no-op; confirm = jobs deleted, panels refresh.
• Open #cost — page renders with current rates, formula, and 30-day breakdown.

Asset cache-busts: app.js?v=17, styles.css?v=14.