Fix VS Code Copilot hook gating regressions

[Siddhant-K-code]

Summary

• Replace version-only native hook gating with runtime capability checks
• Keep legacy Copilot listeners enabled for Insiders, WSL/remote extension hosts, non-desktop hosts, or when chat.useHooks is not enabled
• Add focused VS Code extension tests for the gating matrix

Fixes #1379.
Fixes #1188.
Refs #1020.

Validation

Run from the VS Code extension package on this branch:

cd agent-support/vscode
npm ci
npm run compile
npm run lint
npm test

Expected outcomes:

• npm ci installs the pinned extension dependencies from the lockfile.
• npm run compile exits cleanly with no TypeScript errors.
• npm run lint exits cleanly with no ESLint failures.
• npm test passes the extension test suite, including the Copilot hook-gating matrix.
• The gating tests verify native hooks suppress legacy listeners only when supported, while Insiders, remote/WSL, non-desktop hosts, or disabled chat.useHooks keep legacy checkpoint listeners active.

Additional whitespace check from repo root:

git diff --check origin/main..siddhant/copilot-vscode-hook-gating-regressions

Expected outcome: no output and exit code 0.

Docs

No docs change needed. This is automatic extension runtime detection behavior; no user-facing command or configuration changed.

Notes

PR for focused review and CI validation.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.