feat(discover): disable Discover settings while discovery is switched off

[linroid]

What changed

• On Settings → Discover, everything under the AI discovery switch is disabled while the switch is off: content filter, page access (mode, trusted sites, Add), provider chips, API key, model, endpoint, Test and web search. "Disabled" means greyed out and not clickable or editable; no values change, and what was entered is still there when the switch is turned back on. The switch itself stays usable.
• While it's off, the status line under the switch reads "Lets Discover find downloads for you." before naming any missing key or search credentials, and the settings list summary reads "Off" rather than "Not set up". Nothing below the switch can be changed then, so prompting to finish setup would be misleading.

Why

Since #378 discovery is on by default and the switch is how users opt out. Leaving the form editable while it's off suggested the settings were in effect.

Notes for reviewers

• This drops one behaviour: Test used to work with the switch off so a key could be checked before turning discovery on. Now it needs the switch on. docs/ai-discovery.md is updated. AiSettingsController.testConnection still supports a switched-off test; only the UI no longer offers it.
• The render test checks the controls carry the disabled semantics rather than clicking them, because firing a click through semantics bypasses Compose's enabled = false. Real pointer and touch input is blocked.

Testing

• ./gradlew :app:shared:jvmTest passes.
• New tests:
  • AiDiscoverySettingsRenderTest.switchOff_disablesEverythingButTheSwitch: switching off disables the page access field, provider chips and access menu but not the switch; switching back on re-enables them and keeps the trusted sites.
  • SettingsPageTest.discoverSummary_switchedOffWithoutKeys_saysOff.
• New snapshot settings-discover-off, rendered with -Psnapshots and checked.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-04T09:53:25.628458Z	fea9709	PR opened

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[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.