feat: persist chat deprecation acknowledgement

[araarush]

Problem

The shared Amazon Q chat client emits an acknowledgement when the IDE end-of-support notice is dismissed, but VS Code did not persist or return that acknowledgement. Without client-side state, the notice can return after the extension host restarts.

Companion shared-client change: Amazon-Q-Developer/language-servers#2877.

Solution

• Add a dedicated amazonQChatDeprecationNotice suppression setting.
• Pass deprecationNoticeAcknowledged to the shared chat client when creating the webview.
• Persist acknowledgements for the client-deprecation-notice message ID.
• Keep this state independent from the previous pair-programming feature card.
• Add unit coverage for acknowledged and unacknowledged initialization and dismissal handling.

Validation

• Focused Amazon Q chat unit suite: 11 passing.
• Tested with production-shaped local Flare manifest version 1.79.924.
• Verified the notice appears in new chats before acknowledgement.
• Verified dismissal is reflected across open and future chats.
• Verified dismissal remains persisted after a complete VS Code process restart.

Video

Screen.Recording.2026-09-23.at.12.03.53.PM.mov

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• License: I confirm that my contribution is made under the terms of the Apache 2.0 license.

[dungdong-aws]

nit: can we have some acknowledge button a pop-up instead of silently acknowledge through X

[araarush]

On the acknowledgement behavior: Product confirmed that the X is the shared dismissal behavior across all IDEs. It is an explicit user action: Mynah emits the shared client-deprecation-notice acknowledgement, and each IDE client persists that same dismissal so the notice stays hidden across restarts. Adding a separate button or pop-up in VS Code would diverge from the product-approved cross-client behavior.

[dungdong-aws]

sgtm!