fix: run workspace updates in interactive task

[EhabY]

Summary

• Runs coder update through an interactive VS Code task when CLI update is supported, so parameter prompts can be answered in a real terminal.
• Keeps the existing API fallback for environments without CLI update support.
• Returns the fresh workspace after update and carries it through the connection state machine before agent readiness checks.

Fixes #939.

Tests

• pnpm test:extension ./test/unit/api/workspace.test.ts ./test/unit/remote/workspaceStateMachine.test.ts
• pnpm typecheck
• pnpm lint
• pnpm format:check
• pnpm build

Supporting plan and decision context

The issue is caused by coder update prompting for parameter values while the extension streams CLI output to a read-only VS Code OutputChannel.

Chosen approach: use a VS Code Task with ShellExecution for updates so the CLI keeps owning parameter resolution and prompts, while the extension can await task completion via vscode.tasks.onDidEndTaskProcess.

Why this path:

• --use-parameter-defaults is insufficient because required parameters without defaults still need input and the flag is version-dependent.
• Reimplementing dashboard-style parameter prompts in the extension is larger and risks diverging from CLI/API behavior, especially for dynamic parameters.
• A VS Code task provides an integrated terminal and completion events, which is a better fit than a read-only output channel or a plain terminal without reliable completion detection.

Non-goals:

• Do not change when the update happens; it still runs after window reload during remote setup.
• Do not build a custom parameter editor in VS Code.
• Do not change the coder start path.

Generated by Coder Agents.