v1.25.4 — Retire Excel model controls

Remove the retired Excel Models configuration surface.

• Remove its panel, navigation, search entries, state, and localized text.
• Clean obsolete Excel configuration on visual save while preserving other provider settings, private instructions, and client keys.
• Preserve the existing fork layout and remaining configuration controls.

Companion API: v7.2.179.

Validation: 448 tests, lint, type-check, versioned production build, independent staged audit, and browser verification.

Published management.html matches the reviewed v1.25.4 artifact byte-for-byte and is acquired/served correctly by both published API binary variants tested.