[Chore] Clean up skipped extension package tests

[roomote]

Opened on behalf of Elliott de Launay. View the task or mention @roomote for follow-up asks.

What problem this solves

Resolves stale skipped coverage in the extension-package tests around project MCP settings, Task request shaping, and retry handling. Those skips were masking current behavior and leaving a mix of obsolete expectations and still-important flows unverified.

Why this change was made

The MCP settings tests were updated to match the current file creation and translated error behavior, the Task coverage was rewritten at narrower and more stable seams, and the obsolete ContextProxy integration block was removed. The retry assertions now follow the current auto-approval and structured backoff flow instead of the legacy retry strings and flags.

User impact

No user-facing product behavior changes. CI and future test work get clearer signal from the extension-package suite, with fewer stale skips and coverage that matches the current implementation paths.

[roomote]

No actionable issues found. See task

• Task.spec.ts now calls buildCleanConversationHistory() / maybeRemoveImageBlocks() directly, so it no longer proves attemptApiRequest() applies those transforms before api.createMessage().
• ClineProvider.spec.ts seeds currentWorkspacePath directly, so it no longer verifies that openProjectMcpSettings uses the real active workspace state.
• CI is no longer pending: e2e-mock.
• CI is no longer pending: knip.
• CI is no longer pending: platform-unit-test (ubuntu-latest).
• CI is no longer pending: platform-unit-test (windows-latest).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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