Target: https://github.com/pingdotgg/t3code/pull/19898
Reviewed local head: 69e9b1c4e506b064aaa82a8bfaff31f3605b6b44
Comparison base: 1451e7cb23034d29774338608368a15d8845df36

Before: focused fixed-base negative control failed both replacement regressions (2 failed, 56 passed): file URLs lacked a position and query state had no confirmed-file classification.
After: 58/58 focused tests in four existing files pass. Two new behavior tables cover 13 URL/state rows; all 56 preexisting tests retained. Web and contracts typecheck, six-file lint and formatting pass.

Integrated headless proof through T3 Browser panel, isolated worktree dev app/server: opened the existing server project src/bin.ts preview and performed a real project file read. Applied an in-memory EnvironmentPresentation fixture to select remote-links with proof-remote.local, and installed an openExternal capture at the shell boundary. Neither fixture sets file classification nor changes URL generation. Clicking the actual Open file in preferred editor button captured:
vscode://vscode-remote/ssh-remote+proof-remote.local/home/ubuntu/wt/terminal-preview-18/apps/server/src/bin.ts:1:1
This proves real query -> FilePreviewPanel -> OpenInPicker -> URL builder -> dispatch boundary on reviewed production bytes, with controlled remote presentation/dispatch fixtures. It does not prove a real SSH connection or OS editor launch.

Folder, omitted flag, Zed and JetBrains links plus pending, transient cached error, binary and directory states are covered by the behavior tables. They were not all driven live. Initial app startup exceeded two 45-second waits, then loaded. A live base comparison was attempted by temporarily restoring four production files to fixed base; hot reload restarted the app and the click timed out, so no live baseline capture is claimed. Reviewed files were restored byte-for-byte and git status is clean. The before proof is the negative-control tests, not a reconstructed screenshot. The UI appearance is unchanged; behavior is the emitted URL.

Human follow-up: from a genuinely remote web connection and an Electron client with a configured SSH route, preview a confirmed text file and a binary file, select VS Code, and verify each opens as a file without ENOTDIR; open the project/folder picker and verify it opens a folder. Repeat after a transient refresh failure. Check native OS URL dispatch on macOS/Windows/Linux; native VS Code/Remote-SSH, Electron, macOS, Windows, iOS and Android were not exercised here. Mobile has no editor-link path changed by this PR.