refactor: remove six private declarations nothing references

[trac3r00]

Summary

Removes six private / fileprivate declarations that nothing references. Swift does not warn about unused private functions or constants, so these were left behind when their callers changed:

File	Removed	Notes
App/MenuBarRenderer.swift	metricItems(for:metrics:preset:) (128 lines)	Superseded by the per-metric rendering. MetricItem stays in use.
Services/Switcher/WindowActivator.swift	restoreSourceAfterTargetMinimize(_:)	Replaced by restoreSourceAfterTargetMinimizeIntent. SwitcherSupport.shouldRestoreSourceAfterTargetMinimize is still used there.
App/StatusItemController.swift	maxPlacementGeneration	Only StatusItemPlacementSupport.maxPlacementGeneration is read.
UI/Settings/HomebrewSettings.swift	updateHelp(_:)	The used copy lives in PanelHomebrewView.
UI/Media/MediaWorkspaceView.swift	setInput(_:)	Every caller uses setInputs(_:).
UI/Settings/RadialMenuVisualCanvas.swift	chipSize	The wheel uses RadialMenuLayout.chipSize.

No behavior changes: each removed symbol was private to its file, and the build shows nothing referenced them. Net: 160 lines deleted, nothing added.

I found these by scanning Sources/ for private declarations whose name appears only once in their file, then checked Tests/ and generate_sources.py for references by name. A second scan after the removal found no newly orphaned private declarations.

Verification

• ./build.sh --dev: 0 warnings. ./build/VorssaintDeveloper --selftest: SELFTEST OK, on MacBookPro18,3, macOS 26.6.2.
• ./build.sh --test: 61,538 checks, the same count as main, with 17 failures. They are the same 17 cases (NotchCompactTests.swift:251 and SwitcherScrollTests.swift:163) that fail on an untouched main while this Mac's screen is locked. main passed all of them before the lock.
• git diff --check: clean.