Exclude customer-facing Deprecated AI models from default extension framework model selection

[Copilot]

The AI model service filtered out retired versions but still returned ARM lifecycleStatus: "Deprecating" models by default. Per the ARM Models lifecycle mapping, Deprecating is the customer-facing Deprecated stage (existing customers only, new deployments blocked), so it should not be offered as an available/recommended choice for new deployments.

Changes (cli/azd/pkg/ai)

• Default exclusion — convertToAiModelsAt now excludes versions whose lifecycle status is ARM Deprecating (Deprecated) or Deprecated (Retired) in the default view, in addition to the existing inference-expired and SKU-level filtering.
• Opt-in preserved — FilterOptions.Statuses is the opt-in path: callers requesting ["Deprecating"] (e.g. existing-customer management) get exactly those statuses. This also fixes a latent bug where Deprecated versions were dropped before the status filter could match them.
• Retired always excluded — versions with deprecation.inference <= now (410 Gone) are excluded unconditionally, regardless of requested statuses, matching the docs' guidance to treat past inference dates as retired regardless of lifecycle lag.
• Helper renames to avoid colliding with ARM terminology: modelLifecycleDeprecated → modelLifecycleExcluded, modelDeprecationReached → modelInferenceRetired, modelVersionDeprecated → modelVersionExcluded.
• Docs/proto — updated FilterOptions.Statuses (Go + ai_model.proto) to document default exclusion and opt-in semantics.

Check ordering in convertToAiModelsAt:

// Always drop retired inference endpoints (410 Gone), regardless of requested statuses.
if modelInferenceRetired(m.Model.Deprecation, now) {
    continue
}
if len(statuses) > 0 {
    // Opt-in: return only requested lifecycle statuses (incl. Deprecating/Deprecated).
    if !slices.Contains(statuses, modelLifecycleStatusValue(m.Model.LifecycleStatus)) {
        continue
    }
} else if modelLifecycleExcluded(m.Model.LifecycleStatus) {
    // Default view excludes customer-facing Deprecated (Deprecating) and Retired (Deprecated).
    continue
}

Tests

• Updated existing aggregation/helper tests to reflect that Deprecating is excluded by default.
• Added TestConvertToAiModels_ExcludesDeprecatingByDefaultButAllowsOptIn using the issue's gpt-4.1-mini data (Deprecating + future inference): excluded by default, returned when Statuses: ["Deprecating"] is requested.