[r3dbars]

Addresses UI-SETTINGS-A-10 and its exact duplicate UI-SETTINGS-B-7 in one canonical PR.

Remove the unused RetainedDataSourceComboBox, its dedicated lifetime fixture, its fast-source entry and the stale guide clause. The name field became an NSTextField in merged #2263; exhaustive tracked source/test/script/config references found no app caller for the combo box. The four current SpeakerNameAutocompleteField callers, suggestion behavior and Speakers review/rename/merge/delete flows are unchanged. The historical source-pin inventory retains its original conversion record and adds one factual retirement sentence so it no longer presents the removed fixture as live. Broad #2336 only acknowledges this component's lack of app users in the guide; this PR contains the standalone removal and leaves that broad PR untouched.

Validation:

• Independent root full-diff/source review: GREEN. Removed definitions/test-only references were read in full; no remaining code/test/script/config references to the removed class, setter, stub or NSComboBox.
• No new test is needed for unused-component removal. The native current naming-field suite was not run: it opens/focuses windows and synthesizes events.
• Initial canonical run preserved a documentation-pointer failure for the retired fixture; the reviewed historical-row annotation corrects that reference without changing checker rules, counts or baselines.
• Final immutable bash check.sh: 25 PASS, one orchestration preflight SKIP, and full fast suite explicitly BLOCKED (exit 3), leaving the overall result FAIL. App build, strict-concurrency census, source lists, module boundaries, source pins and documentation paths passed. No baselines grew. Raw proof archived before verifier, bound to clean/stable head eb382b08a833f95bde429102051bc616736bdb2a.
• Standalone preflight passed. Verifier rebuilt the app successfully; UI and speed were both SKIP because Transcripted was already running. Nothing was quit or launched, so this supplies no native interaction or launch-speed proof.

Actual native naming interaction remains unverified; no UI/audio/model/account flow was executed. No result from another head or frozen integration cut is claimed. No policy, merge or release change.