Show one consistent state in Settings > Search while a change applies and after #2245

Part of #2091 (AI-4694).

Classification: Reported defect. Priority: Low.

Problem

The desktop app's Settings › Search tab shows contradictory or stale state around a change.

• While the built-in model is being applied, the header (SearchCurrentText) says "Search changes have not been applied yet.", and the apply button is relabelled "Try again" (disabled), as if something had failed. At the same time the panel shows "Setting up search…" and "Search by meaning with the built-in model.".
• No download progress appears for the 322 MB model: no SearchProgress or SearchPullText in the 20 s after Save. Here the model came from a local feed in about 3 s, so on a real connection the user would see a long wait with no progress.
• The summary goes stale after switching back to keyword search. It kept reading "The search index for saved information is being built with the built-in model in the background." for about 3 minutes, long after the server had finished.
• The keyword-mode header is vague: "Searches by keyword unless the server's own settings choose a model."

The change itself worked both ways: "Searches by meaning with the built-in model.", then back to keyword.

Evidence

Windows local edition from main, 2026-11-01, walkthrough search-by-meaning steps 5 and 9. Desktop app 1.4.1-beta.2.12, local server bundle 1.4.1-main.20261101, Windows Sandbox.

Acceptance

• While a change is applying, the tab shows one consistent "applying" state, with no "Try again" and no "not applied yet".
• The model download shows progress whenever it takes more than a moment.
• The summary follows the server's state while the tab is open.