Fix Ctrl+wheel zoom in agent panes

[Dinah Xiaoman G (DinahK-2SO)]

Summary of the Pull Request

Makes Ctrl+mouse-wheel zoom text in agent panes before VT mouse tracking can consume the event. Plain and horizontal wheel input still reaches the agent, while ordinary terminal and Ctrl+Shift opacity behavior remain unchanged.

References and Relevant Issues

Closes #790

Detailed Description of the Pull Request / Additional comments

Agent panes run a mouse-tracking TUI, so the existing VT-first wheel route consumed Ctrl+wheel as chat scrolling. Agent TermControls now opt into a vertical Ctrl+wheel priority path. The default route remains unchanged. The PR also adds physical HWND wheel injection to ItE2E and release-checklist case C295.

Validation Steps Performed

• Focused and neighboring Control unit tests passed, including vertical, plain, horizontal, default, and Ctrl+Shift wheel paths.
• Exact publish package built and deployed with matching source/live binary hashes.
• Official C295 packaged E2E passed 1/1.
• Physical terminal/agent wheel suite passed 3/3 with fresh screenshots.

PR Checklist

• Closes Ctrl+scroll doesn't zoom, and behaves differently in the agent pane #790
• Tests added/passed
• Documentation updated
• Schema updated (if necessary)

[Copilot]

🟡 Changes recommended

The new Win32 GetCursorPos P/Invoke is missing SetLastError=true, so failures can report incorrect Win32 error codes in the new wheel-injection helper.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Fixes Ctrl+mouse-wheel zoom behavior in agent panes by letting agent TermControls prioritize zoom handling before VT mouse tracking consumes vertical Ctrl+wheel, while keeping plain wheel and horizontal wheel routed to the agent as before.

Changes:

• Add an agent-only “prioritize zoom on Ctrl+vertical wheel” path in ControlInteractivity::MouseWheel, wired through TermControl via a new opt-in flag.
• Enable this behavior for agent panes and extend Control unit tests to cover VT-mouse-enabled routing vs. zoom priority.
• Add ItE2E support for physical wheel injection and an E2E + release-checklist case validating Ctrl+wheel zoom + plain wheel chat scrolling.

File summaries

File	Description
test/e2e/tests/Feature.AgentMouse.Tests.ps1	Adds a physical wheel routing E2E validating plain wheel scroll + Ctrl+wheel zoom in agent panes.
test/e2e/README.md	Updates E2E suite table entry and coverage/test-status counts to include the new case.
test/e2e/ItE2E/Public/Ui.ps1	Adds Win32 SendInput-based physical wheel injection helper (Invoke-WtWindowWheel).
test/e2e/ItE2E/ItE2E.psm1	Exports Invoke-WtWindowWheel from the ItE2E module.
src/cascadia/UnitTests_Control/ControlInteractivityTests.cpp	Adds a unit test ensuring agent-pane Ctrl+wheel zoom happens before VT mouse wheel routing.
src/cascadia/TerminalControl/TermControl.idl	Introduces EnableAgentMouseWheelZoom API to opt TermControl into the new behavior.
src/cascadia/TerminalControl/TermControl.h	Stores the per-control agent zoom-priority flag.
src/cascadia/TerminalControl/TermControl.cpp	Passes the new flag into interactivity mouse-wheel handling paths.
src/cascadia/TerminalControl/ControlInteractivity.h	Adds a MouseWheel(..., bool prioritizeZoom) overload.
src/cascadia/TerminalControl/ControlInteractivity.cpp	Implements the zoom-priority fast path ahead of VT mouse routing when enabled.
src/cascadia/TerminalApp/AgentPaneContent.cpp	Enables the agent zoom-priority flag on agent-pane TermControls.
doc/release-check-list.md	Adds release-checklist case C295 covering physical Ctrl+wheel zoom in agent panes.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

🔵 Needs a closer look

The new physical-wheel E2E path should include the same foreground/interactive-desktop skip gating used elsewhere to avoid flakiness in unattended or focus-contended runs.

Review details

Suppressed comments (2)

Previously missed (2) — in code that hasn't changed since the last review.

test/e2e/tests/Feature.AgentMouse.Tests.ps1:213

• This physical wheel test currently fails hard when the WT window cannot take foreground (locked desktop / competing foreground app), which can make the suite flaky in unattended runs. Mirror the existing hotkey/physical-input suites by skipping when Test-WtWindowKeyFocusable fails before sending wheel input.
  test/e2e/ItE2E/Public/Ui.ps1:124
• Avoid the raw 0x0800 magic number for mouse-wheel injection; define and use a named constant so the SendInput flags are self-describing and less error-prone to extend (e.g., if adding HWHEEL later).

• Files reviewed: 12/12 changed files
• Comments generated: 0 new
• Review effort level: Lite

[Copilot]

🔵 Needs a closer look

The updated E2E coverage counts in test/e2e/README.md leave a nearby sentence still referring to the old “147 implemented checklist items,” creating an inconsistency that should be corrected.

Review details

Suppressed comments (1)

Previously missed (1) — in code that hasn't changed since the last review.

test/e2e/README.md:64

• The updated coverage/test-status counts (148/150 and 128 baseline cases) are followed by a sentence that still says "The 147 implemented checklist items...", which is now inconsistent and can confuse readers tracking coverage.

• Files reviewed: 12/12 changed files
• Comments generated: 0 new
• Review effort level: Lite

[Copilot]

🟢 Approval recommended

The behavior change is narrowly gated to agent panes, and the PR adds both unit and physical E2E coverage plus a release-checklist item for the regression.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 0 new
• Review effort level: Lite