Nodes and sessions UI: fast, calm, and clear about what each action does

Goal: the Nodes, MicroVM, Worktrees and Audit › Sessions surfaces load quickly and keep red for real failures. They show what holds a slot, and make plain what a destructive action really ends. Items are examples. Decline any that is no longer present. Consolidates drafts 7895 (items 1–5), 7913 (item 3) and 7892 (items 3, 5, 6). 1. Node detail in the 1280px split pane sits on "Loading…" for about 15 s, while the full page renders at once. Make them equally fast. 2. Node overview says "Runners 0" while a task holds a slot. Show held slots and their holder ("1 slot held by #4815"). 3. A rented Jaah Cloud node has two Delete paths: the node page ("instance is TERMINATED") and the billing hosting page (credits unused days). On a rented node, route Delete to the hosting delete, or say which one ends the rental. 4. The Node › Delete confirm is a 9-line wall of text at 390px. Cut it to a few scannable facts (slots deleted, sessions killed, instance terminated, can't be undone). 5. Add node › Jaah Cloud › Shared says only "No shared capacity right now". Suggest Dedicated, or say when capacity returns. 6. Audit › Sessions colours "waiting for upload" red. Use a calm tone for waiting. 7. Audit › Sessions: the "Running" filter lists rows the page shows as ended (`attempt_over`). Apply the same rule server-side. 8. Attempts with no session repeat the same cause and node on every row. Group them ("7 × process crashed on vis-kvm-1"). 9. MicroVM › VMs on the node: a VM id wraps in the 541px pane. Truncate it with a tooltip and copy button, like layer keys. Out of scope: liveness, ingest and transcript upload logic; the MicroVM runtime; billing rules. Done means: - Each item fixed or declined with a reason; screenshots at 1280px and 390px. Required checks: ./dc check full

All 9 items fixed in PR #6241, queued in the merge lane: pane load starvation, slot holders, short delete facts plus the rented-node path, a Choose Dedicated button, calm waits, server-side Running filter, grouped attempts, VM id truncation. Quick gate and changed-area tests green; screenshots checked at 1280px and 390px. Follow-ups: draft #7985.