Release completed webview message reply callbacks

[Henning Dieterichs (hediet)]

Summary

Release message reply callbacks as soon as each request completes instead of retaining them for the lifetime of the webview.

• Replace the pending-reply record with a Map.
• Delete an entry before resolving or rejecting its reply.
• Remove the entry if sending the request throws synchronously.
• Ignore duplicate/unknown replies rather than dispatching their payload as a command after cleanup.
• Test pending-entry counts, successful and failed replies, synchronous send failures, and command routing.

This is a standalone fix against main, extracted from #9047 to keep that PR focused on host/context ownership. No host injection, singleton removal, or Component Explorer tooling is included here.

Validation

• npm run test:webviews: build succeeded; 65 tests passed, including two new cleanup regressions.
• npm run lint and npm run hygiene passed.
• Existing quote-reply listener warnings are addressed separately in Fix webview comment and stack action lifecycle #9049.
• No dependency or lockfile changes.

[Copilot]

🟢 Approval recommended

The focused implementation matches the stated behavior and includes adequate regression coverage.

0 open findings

What changed in this PR

Updates webview request handling to release completed reply callbacks promptly.

Changes:

• Stores pending replies in a Map and removes them before settlement.
• Cleans up synchronous send failures and ignores duplicate or unknown replies.
• Adds regression coverage for success, rejection, cleanup, and command routing.

File	Description
webviews/​common/​message.ts	Implements pending-reply lifecycle cleanup.
webviews/​common/​test/​message.test.ts	Tests reply cleanup and routing behavior.

🧠 Review effort: Balanced

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