ci: disable the swift Dependabot ecosystem until its image ships Swift 6.4

[KevinTCoughlin]

The problem

Dependabot's weekly swift run has failed every week since 2026-08-10 — seven consecutive runs — producing no PRs and no notification. A failed Dependabot run isn't a failed check on anything, so there's no red X anywhere; it's only visible via gh run list.

error: 'browsefeaturecore': package 'browsefeaturecore' is using Swift tools
version 6.4.0 but the installed version is 6.3.1

Dependabot resolves Swift packages inside its own container, and dependabot-core's swift/Dockerfile pins ARG SWIFT_VERSION=6.3.1. All 19 manifests under Packages/ are swift-tools-version: 6.4, so resolution aborts before reading a single dependency.

Why not just lower the tools version

Not available — and not for a taste reason. The manifests use PackageDescription API that doesn't exist before 6.4:

• .iOS(.v26) as a platform
• swiftSettings: [.defaultIsolation(MainActor.self)] in BrowseFeatureCore and SearchFeatureCore

A 6.3 toolchain wouldn't parse them. That would trade a failing updater for a tree that doesn't build.

What this does

Disables the ecosystem, commented out verbatim rather than deleted. The comments on that block are load-bearing — which directories exist only because Factory is exact-pinned and must move as a group, and why PlaybackEngineAudioStreaming is listed separately since #122. Re-deriving that later is how the factory group silently stops covering a directory.

Adds dependabot-swift-watch.yml to close the gap that disabling opens. Factory is exact: "3.3.2"-pinned in seven manifests and AudioStreaming exact: "1.4.4" in an eighth, and nothing watches them now — trading a silent failure for a silent gap would be no improvement. The watch polls that ARG SWIFT_VERSION line weekly and opens a single issue when it reaches 6.4. Same shape and reasoning as the existing runner-image-watch.yml; it costs ~15s of free ubuntu time.

It errors rather than reporting no-change if the ARG line ever moves upstream — a watch that quietly stops watching is precisely the failure it exists to prevent.

Verification

• Extraction returns 6.3.1 against the live upstream Dockerfile.
• sort -V comparison checked across 6.3/6.3.1/6.4/6.4.0/6.5/6.10/7.0/5.9 — 6.10 correctly ranks above 6.4.
• actionlint clean on the new workflow (and on the unmodified runner-image-watch.yml as a baseline).
• .github/dependabot.yml still parses; github-actions remains the only active ecosystem.

Note: this and runner-image-watch.yml are now waiting on the same Swift 6.4 / Xcode 27 transition from different directions. Neither should be closed assuming the other landing settled it.

🤖 Generated with Claude Code

https://claude.ai/code/session_013U8tNXdjZpFPUTWpABee5y

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None