fix: align Firefox minimum version with manifest capabilities

[alectimison-maker]

Summary

• Raise the Firefox desktop minimum from 109 to 140.
• Add a regression test that ties the declared minimum to the packaged tabGroups and AMO data-collection manifest capabilities.
• Remove stale numeric minimums from explanatory comments so the manifest remains the source of truth.

Motivation

The Firefox package declared support for Firefox 109 even though it now includes storage.session (Firefox 115), the tabGroups permission (Firefox 139), and browser_specific_settings.gecko.data_collection_permissions (Firefox 140 on desktop). Mozilla web-ext lint reports this mismatch against the declared minimum.

See #2793 and the Mozilla references linked there.

Design

The manifest minimum is raised to the newest capability required by the desktop package. Runtime feature detection around tab grouping remains unchanged. Raising the declared minimum is preferable to broad fallback work here because runtime guards cannot make an unsupported manifest permission or manifest key compatible with Firefox 109.

The regression test validates the complete dotted-numeric version and checks it against the known manifest capability floors.

Testing

• npm test — passed (33 toolbar guard tests, 1693 main tests, 60 security checks)
• npm run test:fixtures — passed (165 tests)
• npx --yes web-ext@latest lint --source-dir src/firefox --output json — 0 errors, 0 notices; desktop minimum-version findings cleared
• git diff --check upstream/main...HEAD — passed

Unavailable browser check:

• Manual unpacked Firefox load — not run because no Firefox installation is available in the test environment. web-ext lint is reported separately and is not treated as a runtime browser check.

Compatibility and risks

Firefox versions below 140 will no longer install the extension. This makes package metadata match capabilities already shipped; it does not remove support that the current package can reliably provide.

Mozilla lint still reports existing general warnings and one Firefox Android-specific compatibility warning. The current Firefox package targets the desktop sidebar, so Android support is not expanded in this change.

Scope

• No Chrome or Edge behavior changes.
• No Firefox runtime tab-group behavior changes.
• Firefox Android support and unrelated linter warnings remain out of scope.

Closes #2793

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[Copilot]

Pull request overview

Aligns Firefox installation compatibility with manifest capabilities requiring Firefox 140+.

Changes:

• Raises Firefox’s minimum version from 109 to 140.
• Adds regression coverage for manifest capability version floors.
• Removes stale minimum-version references from documentation comments.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
test/run.js	Tests Firefox manifest version compatibility.
src/firefox/manifest.json	Sets Firefox minimum to 140.0.
src/firefox/src/agent/agent.js	Removes stale Firefox 109 reference.
src/firefox/ARCHITECTURE.md	Updates compatibility documentation.

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