[CmdPal] Per-provider search weight (Lower/Normal/Higher)

[michaeljolley]

Phase 3 of the stacked CmdPal search overhaul. Based on and targeting dev/mjolley/frecency-redesign (phase 2), NOT main.

What

Adds a per-provider Search weight (Lower / Normal / Higher, default Normal) that nudges main-page search results within their relevance tier only. Tier always dominates; the weight can reorder near-ties but can never move an item across a tier boundary.

Changes

• ProviderSettings: new ProviderSearchWeight enum (Lower = -1, Normal = 0, Higher = 1) + SearchWeight property. Missing/legacy JSON deserializes to Normal.
• MainListRanker: ProviderWeightBonus = 5.0 constant and ProviderBonus(weight) mapping (signed magnitude). Half a point of lexical quality (LexicalScale = 10), so it only breaks near-ties.
• MainListPage.ScoreTopLevelItem: resolves each item's provider weight (top-level commands by their provider id, installed apps by the well-known AllApps provider) and feeds it into the within-tier score. Backward-compatible optional parameter.
• ProviderSettingsViewModel + ExtensionPage.xaml: a Lower/Normal/Higher ComboBox per provider (shown for built-ins and apps too). New resw strings. Ran applyXamlStyling.

Design constant

• Provider bonus per level: +/- 5.0 points (Higher = +5, Normal = 0, Lower = -5), vs LexicalScale = 10 per lexical point and FrecencyScale = 1. Modest by design.

Tests (all green, x64 host)

• Provider weight reorders within a tier; never crosses a tier boundary (even Higher + heavy history vs a Lower exact match).
• Default Normal == the previous provider-unaware behavior (no-op).
• Applies to app-style (non-TopLevel) items.
• Serialization round-trips; legacy JSON without the property defaults to Normal.
• Build CommandPalette.slnf x64/Debug = exit 0. ViewModels 157/157. All other CmdPal unit suites pass (Registry + WindowWalker not run - known pre-existing non-green).

Atomic to phase 3; host-side only, no extension SDK changes.