[Bug] VSCode: Background subagents no longer surface permission prompts or show task progress (v2.1.47)

Bug Description

Background subagents spawned via the Task tool in the VSCode extension no longer:

1. Surface permission prompts to the user — file writes and tool calls are silently denied instead of showing the approval UI
2. Show task progress — subagents appear as instantly completed (green circle) with zero visibility into intermediate tool calls or status

Both behaviors worked in previous versions. This is a regression introduced in v2.1.47 (released ~Feb 19, 2026).

Related: #13890

That issue covers silent write failures more broadly (since Dec 2025). This issue is specifically about the VSCode extension's UI integration breaking for background subagents — permission prompts and progress indicators no longer render.

Environment

• Platform: macOS (Darwin 22.6.0)
• IDE: VSCode
• Claude Code CLI version: 2.1.47
• VSCode extension version: anthropic.claude-code@2.1.47

Reproduction Steps

1. Open Claude Code in VSCode
2. Spawn a background subagent that needs to write a file:

``
Task(
subagent_type="general-purpose",
run_in_background=true,
prompt="Create a file at ./test-write.md with content 'Hello World'"
)
``

1. Expected: VSCode shows permission prompt for the Write tool, subagent progress is visible
2. Actual: No permission prompt appears. Subagent reports "Both the Write tool and Bash are being denied." Task appears instantly as a green circle with no intermediate visibility.

Observed Behavior

• The subagent runs and attempts to use Write/Bash tools
• Instead of surfacing a permission prompt in the VSCode UI, the tools are silently denied
• The subagent sees denial and reports it can't write, but the user never gets a chance to approve
• In the VSCode task list, the subagent shows as complete immediately — no progress updates, no tool call visibility
• Workaround: Passing mode: "bypassPermissions" on the Task call allows writes, but this shouldn't be necessary — the user should be prompted

What Changed

This worked in prior versions (~2.1.3x range). Background subagents would:

• Surface permission prompts through the VSCode UI when they needed Write/Bash/MCP approval
• Show intermediate progress (tool calls, status) in the task panel

Both broke simultaneously in v2.1.47.

Impact

This effectively breaks all background subagent workflows that need to write files, unless bypassPermissions is used as a workaround. Users lose all visibility into what background agents are doing.