Deprecate and Remove `glab duo ask` from the GitLab CLI
### Deprecation Summary
_Add a brief description of the feature or functionality that is deprecated. Clearly state the potential impact of the deprecation to end users._
`glab duo ask` is a feature of the GitLab CLI that allows git commands to be generated from natural language. Deprecation and removal of this feature will provide a warning that the command is no longer support and future removal will stop it from working entirely.
[Documentation on feature being deprecated](https://docs.gitlab.com/cli/duo/ask/)
#### Migration guidelines
Customers who wish to continue using this kind of interaction can migrate to `glab duo cli` where there is a full agentic chat experience.
#### Background
_Describe why deprecation of this feature is necessary._
### Breaking Change?
<!-- Any change counts as a breaking change if customers need to take action to ensure their GitLab workflows aren’t disrupted. -->
Does this deprecation contain a breaking change? Yes
<!-- If yes:
- Add the ~"breaking change" label to this issue.
- Add instructions for how users can update their workflow.
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### Affected Customers
Who is affected by this deprecation: GitLab.com users, Self-managed users, or Dedicated users? (choose all that apply)
- [x] GitLab.com
- [x] Self-managed
- [x] Dedicated
What pricing tiers are impacted?
- [ ] GitLab Free
- [ ] GitLab Premium
- [ ] GitLab Ultimate
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/label ~"GitLab Free" ~"GitLab Premium" ~"GitLab Ultimate"
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### Deprecation Milestone
This deprecation is being announced in milestone: ```19.0```
### Planned Removal Milestone
The feature / functionality will be removed in milestone: ```19.3```
#### Rollout Plan
- DRI Engineers: @garyh
- DRI Engineering Manager: @francoisrose
For `glab duo ask`, we will follow this pattern: set Cobra's `.Deprecated` field with a message pointing to `glab duo cli` and including the scheduled removal date, and set `.Hidden = true` simultaneously so the command no longer appears in help output. This approach requires no custom warning logic — Cobra prints the deprecation message automatically on every invocation.
#### Communication Plan
- DRI Product Manager: @phikai
**Internal Communication Plan**
The deprecation warning surfaced automatically by Cobra at time of invocation is the primary communication mechanism, supplemented by the command being hidden from help output.
**External Communication Plan**
The deprecation warning surfaced automatically by Cobra at time of invocation is the primary communication mechanism, supplemented by the command being hidden from help output.
#### Labels
<!-- Populate the Section, Group, and Category -->
- [x] This issue is labeled ~deprecation, and with the relevant `~devops::`, `~group::`, and `~Category:` labels.
- [x] This issue is labeled ~"breaking change" if the removal of the deprecated item will be a [breaking change](https://docs.gitlab.com/update/terminology/#breaking-change).
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<!-- Identifies that this Issue is related to deprecating a feature -->
<!-- References
- [Internal Resource on Breaking Changes](https://internal.gitlab.com/handbook/engineering/r-and-d-pmo/knowledge-base/all-articles/breaking-changes/)
- [Public Resource on Deprecations, removals, and breaking changes](https://handbook.gitlab.com/handbook/marketing/blog/release-posts/#deprecations-removals-and-breaking-changes)
- [Deprecation guidelines](https://docs.gitlab.com/development/deprecation_guidelines/)
- [Deprecations and removals doc styleguide](https://docs.gitlab.com/development/documentation/styleguide/deprecations_and_removals/)
- [REST API Deprecations](https://docs.gitlab.com/development/documentation/restful_api_styleguide/#deprecations) and [REST API breaking changes](https://docs.gitlab.com/development/api_styleguide/#breaking-changes).
- [GraphQL Deprecations](https://docs.gitlab.com/development/api_graphql_styleguide/#deprecating-schema-items) and [GraphQL API breaking changes](https://docs.gitlab.com/development/api_graphql_styleguide/#breaking-changes).
- [GitLab release and maintenance policy](https://docs.gitlab.com/policy/maintenance/)
- [Review of GitLab deprecations and removals policy & Runner team deprecations and removals process](https://youtu.be/ehT1xBajCRI)
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