fix(web): preserve WSL provider update results after dismissal

[pandec]

Note

Preview of an upstream PR for pingdotgg/t3code. Never merge this; main here is a clean upstream mirror. Close once the upstream PR is open. The branch carries an intermediate design superseded during review; it will be squashed to one commit before the upstream PR.

Problem

The multi-environment (Windows + WSL) provider update popover owns its update request state inside dismissible toast content. Dismiss it mid-update and the request keeps running while its owner unmounts; the sidebar pill only watches primary providers, so success or failure is never reported anywhere. A hung transport is equally silent.

Fix

Split presentation from result delivery:

• The popover stays live and per-environment: each row keeps its own Update trigger and moves through pending, terminal, and Retry states inline. Triggering one environment's update leaves the others actionable.
• Terminal-result delivery is owned by the notification host, which outlives any toast: each dispatch registers a generation-scoped claim (targeted instance ids, dispatch time). Live provider state and the RPC response race to finish it, and Map.delete on the claim is the atomic single-winner — no duplicate toasts, in either arrival order. Snapshots older than the dispatch are rejected, so a previous attempt's state can't be reported as this one's outcome.
• A result toast fires only when the popover is no longer open to show the result itself. A six-minute expiry reports a failure instead of going silent on a hung transport, and interrupted dispatches surface as retryable failures. An unreachable error branch was removed.

Deliberately not in scope: the running-progress duplication between this popover and the sidebar pill for primary providers. These rows are the only progress surface WSL-side providers have, so suppressing them would trade a cosmetic duplication for missing feedback.

Verification

• 57 focused tests, including: exactly-once reporting across RPC-first and live-state-first orderings, stale-terminal-state rejection, request generations across retries, the unchanged outcome, dismissal followed by delivery, results shown in the still-open popover (no toast), expiry, and interruption. One test renders the production notification host, not just the hook.
• Mutation-proofed: removing the delete-as-claim guard fails four tests; removing the recency filter fails the stale-state test.
• vp check and vp run typecheck clean.

[video placeholder: with Windows + WSL connected, click Update on one environment — the popover stays open, that row shows a spinner while the other row stays actionable. Then repeat and dismiss the popover mid-update — the success/failure toast still arrives.]

Related: pingdotgg#7761 (primary-flow result pattern this mirrors), pingdotgg#7425, pingdotgg#6544.

Implemented by gpt-5.6-sol, orchestrated and reviewed (opus + sol panel) in Claude Code (Fable 5).