fix: persist telemetry banner dismissal state across VSCode restarts

[roomote]

This PR attempts to address Issue #9184. Feedback and guidance are welcome.

Problem

The "Help Improve Roo Code" telemetry notice reappears after every VSCode restart, even after being dismissed by the user.

Solution

• Changed the banner dismissal behavior to set telemetry to "disabled" instead of "enabled" when the user clicks the X button
• Fixed the backend telemetry handler to properly check for "unset" state when determining previous opt-in status
• Ensures the telemetry setting is always persisted to global state when the user dismisses the banner

Testing

• All existing tests pass
• The telemetry banner will now stay dismissed after VSCode restarts
• Users can still manage their telemetry preference through the settings

Fixes #9184

---

Important

Fixes telemetry banner to persist dismissal state across VSCode restarts by setting telemetry to "disabled" on dismissal and updating global state.

• Behavior:
  • Changes dismissal behavior in TelemetryBanner.tsx to set telemetry to "disabled" when the user dismisses the banner.
  • Updates webviewMessageHandler.ts to persist telemetry setting to global state upon dismissal.
• Backend:
  • Fixes webviewMessageHandler.ts to check for "unset" state when determining previous telemetry opt-in status.
• Testing:
  • Ensures telemetry banner remains dismissed after VSCode restarts.
  • Users can still manage telemetry preferences through settings.

^{This description was created by for ad4e33b. You can customize this summary. It will automatically update as commits are pushed.}

[roomote]

Rooviewer   See task on Roo Cloud

Review completed. Found 1 issue that needs attention:

• Banner dismissal behavior incorrectly opts users out of telemetry

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[roomote]

Dismissing the banner by clicking X should not opt users out of telemetry. This conflates two different user intents: (1) dismissing a notification vs (2) explicitly opting out of telemetry. When users click X on a banner, they typically mean "don't show this again" not "I'm opting out of the feature." The current implementation forces users who simply want to clear their screen into an explicit opt-out state. Instead, the banner should persist until the user makes an explicit telemetry choice through the settings link, or the banner could be enhanced with explicit "Enable"/"Disable" buttons. Setting to "disabled" on dismiss means users who might have been fine with telemetry are now opted out simply because they wanted to clear the banner.

_{Fix it with Roo Code or mention @roomote and request a fix.}