[VSCodeSweeper MVP — test only] Fix a browser sniff for Firefox support of async clipboard

[egamma]

⚠️ VSCodeSweeper MVP — test only. This draft PR was generated by an AI experiment
(vscodesweeper) inside a personal fork. It is
not intended for microsoft/vscode and is not a contribution proposal.

Upstream issue: microsoft#184958

Change summary

Firefox users on vscode.dev cannot paste because a stale browser sniff bypasses the async clipboard API detection.

Validation

Remove the || browser.isFirefox condition from the supportsPaste declaration and verify the existing clipboard unit tests still pass via scripts/test.sh --grep clipboard; additionally confirm that no other code path relies on supportsPaste being false for Firefox.

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Branch vscodesweeper/fix-184958 · generated fix · review loop runs separately (codex review).

[egamma]

🤖 codex review — round 1

VSCodeSweeper MVP codex cross-review of a copilot-generated fix (fork-only experiment).

No actionable correctness issues were identified in the diff. The change cleanly factors paste support detection for testing and removes the Firefox exclusion as intended.

[egamma]

✅ Round 1: no actionable findings — the review loop converged.

[egamma]

🤖 codex review

VSCodeSweeper MVP review of the generated fix (fork-only experiment). Findings, if any, are for a human to triage — nothing is auto-addressed.

The patch can falsely enable the Paste command in browsers with partial Clipboard API support, causing a visible command that cannot paste. The support check should match the readText capability used by the paste implementation.

Review comment:

• [P2] Require readText before enabling paste — src/vs/editor/contrib/clipboard/browser/clipboard.ts:33-33
  When navigator.clipboard exists but does not expose readText (for example older Firefox/configurations that expose partial Clipboard API support), this now registers the Paste action even though the web implementation later calls clipboardService.readText(), which invokes navigator.clipboard.readText() and just catches a TypeError without pasting anything. Checking only for the clipboard object removes the previous Firefox guard but still needs to verify the actual read capability used by paste.