Confirm dialogs and their page each own half of one submission lifecycle

[lmcorbalan]

User story / Problem statement

Currently EndPendingGrant and CancelGrant each own their write, toast, error and close, stay dismissible mid-submission, and close over values derived outside them. Six review fixes across four waves on PR #197 all landed on that one arrangement.

Expected outcome

Dismissing a confirm dialog over the wallet prompt has no bearing on the submission it started, and whether a dialog is mounted stops being something a write path reasons about.

Acceptance criteria

• The page rendering the list owns the submission, its in-flight set and its toast
• EndPendingGrant and CancelGrant take props and emit onConfirm, holding no submission state
• No onScreen ref, or any other mounted-check, survives in either dialog
• A value a dialog shows cannot disagree with the value its write uses
• Dismissing a dialog mid-submission leaves its card unclickable until the write settles
• pnpm -C dapp/frontend test and pnpm -C dapp/frontend typecheck pass

Alternatives considered

Make the dialog non-dismissible while submitting. Rejected once already: a user cannot see past the wallet prompt, so dismissing it is worth keeping.

Technical notes

The split today: pages/PendingGrants/index.tsx holds endingCids, the refresh and the list; the dialogs hold submitting, the toast and the close. dapp/frontend runs no DOM tests, so review and the manual loop are the verification.

Additional context

Follow-on from PR #197 (#181), under epic #157, whose history holds the six fixes.