[FEATURE] Show incremental/streaming bash command output in VS Code extension

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When Claude Code runs bash commands via the VS Code extension, the entire output is buffered and only displayed after the command completes. For long-running commands (builds, test suites, deployments), the user sees no output for extended periods — just a spinner. This makes it difficult to:

Monitor progress of multi-minute commands
Catch early failures without waiting for full completion
Maintain confidence that the command is actually progressing

Proposed Solution

Add streaming output support for Bash tool calls in the VS Code extension, either:

Always stream — display output lines as they arrive (preferred)
Opt-in setting — e.g. "streamBashOutput": true in settings.json
Threshold-based — buffer short commands, stream commands exceeding N seconds

Alternative Solutions

Workarounds investigated
--verbose CLI flag: Only available in the terminal CLI, not the VS Code extension. Also shows debug/turn logging rather than streaming command output.
Hooks (PreToolUse/PostToolUse): Cannot intercept or redirect the tool's output stream — they only run before/after execution.
run_in_background + manual tail: Works but requires the user to manually coordinate, defeating the purpose of an integrated experience.
claude config set -g verbose true: verbose is not a recognized key in the settings schema, and config set is not a valid subcommand.

Priority

High - Significant impact on productivity

Feature Category

Other

Use Case Example

_No response_

Additional Context

Current behavior
Claude invokes a Bash tool call
VS Code extension shows a spinner with no output
After the command finishes, the full stdout/stderr is displayed at once

Expected behavior
Bash command stdout/stderr streams incrementally into the VS Code extension UI as it is produced, similar to a normal terminal experience.

Environment
Claude Code VS Code extension
Applies to all platforms (Linux, macOS, Windows/WSL)