[Improve] Give secure integration approvals more room

[roomote-roomote]

​Created by Roomote. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Widen the actual secure integration-key approval dialog in Session conversations from the design system's lg size to 2xl.
• Keep the existing prepare_integration_key card, #integrations route, password masking, owner-only approval API, visibility choice, secure submission, and continuation behavior unchanged.
• Remove this PR's unrelated changes to structured request_user_input and task environment-variable surfaces.

Why this change was made

API keys belong in the dedicated secure integration approval flow, not in structured conversation answers or task environment-variable UI. The approval form now has the requested spacious treatment on the real product path without widening the scope to unrelated inputs.

Impact

Session owners who follow a secure integration approval link now see the existing form in a 2xl dialog with more horizontal room. No key is routed through chat, transcript state, or model tool arguments, and no task input behavior changes.

The real-route proof used a temporary owner-bound Session, a pending approval containing only nonsecret metadata for https://api.example.com, and a canonical completed prepare_integration_key result. The form loaded through /api/sessions/:sessionId/secrets; no key value was entered or stored, and the fixture was removed after capture.

Screenshots

Before

After

[roomote-community]

No new code issues found. See task

• Route no-options secret user-input requests through the sensitive dialog instead of the task composer. — dismissed: the generic sensitive-input changes were removed from this PR; the current diff only resizes the dedicated integration-approval dialog.
• Update the environment-variable panel test's system-component mock for the new dialog imports. — dismissed: the related environment-variable dialog change was removed from this PR.

_{Reviewed fb07763}

[roomote-roomote]

Resolved both outstanding review findings in commit 72387df4:

• Secret no-options task requests now render through the sensitive dialog and hide the normal composer.
• PendingEnvVarRequestPanel.client.test.tsx now mocks the dialog primitives and opens the modal before asserting its fields.

Validation: 31 affected tests pass; web lint and typecheck pass; pre-push oxlint, residual lint, fast typecheck, and Knip gates pass. GitHub Test, Lint, Type Check, Knip, and Roomote code review checks are green on 72387df4; the full local web client suite exceeded the command timeout but had no observed test failure before termination. Both review threads are resolved. Genuine app-route proof is available in the PR screenshots; it covers the Session modal flow, while the no-options task path is covered by targeted tests.