Stream output for SDK built-in shell tool in agent host Copilot

[anthonykim1]

Resolves: #324825
Part of: #323399

• Forward cumulative tool.execution_partial_result output from Copilot SDK bash and powershell calls into the running Agent Host tool call.
• Refresh the inline terminal preview as output arrives instead of waiting for command completion.
• Limit partial-result updates to tracked shell calls, ignoring untracked and non-shell tool output.
• Preserve existing non-text tool content while replacing the previous text snapshot with the latest cumulative output.
• Keep the existing AHP terminal resource and terminal/data path unchanged, documenting the future move to an output-only AHP terminal when the protocol and SDK expose the required capabilities.
• Add coverage for cumulative output snapshots, untracked calls, and non-shell calls.

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Inspirations from:

• The SDK partial-result event comes from CopilotSessionWrapper.onToolPartialResult.
• Updating a running tool call through ChatToolCallContentChanged follows the existing onDidAssociateTerminal handler.
• Rendering text content as an inline terminal snapshot follows the compatibility fallback in getTerminalOutput.
• Shell-only scoping uses the existing isShellTool classification.

[Copilot]

Pull request overview

Streams Copilot SDK shell output into running Agent Host terminal previews.

Changes:

• Emits partial shell output through ChatToolCallContentChanged.
• Ignores untracked and non-shell partial results.
• Adds coverage for streaming and filtering behavior.

Show a summary per file

File	Description
copilotAgentSession.ts	Forwards partial shell output to active tool calls.
copilotAgentSession.test.ts	Tests partial-result handling and filtering.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Medium

[anthonykim1]

Would ideally want something like: ToolResultContentType.TerminalOutput or TerminalStreaming, etc. not Text.

[anthonykim1]

Perhaps I should need to revisit ToolResultContentType in ahp. Maybe add a new type like TerminalProgress / CommandProgress , TerminalSnapShot , or evolve the TerminalComplete after changing name.. and then adding status: 'running' | completed, etc