SDK: Promote catalogue search and planning APIs to stable

## Summary

Promote the generated catalogue search and planning surface from preview to a stable Copilot SDK release using an exact schema-bearing CLI package.

Parent: https://github.com/github/copilot-sdk/issues/2106
Epic: https://github.com/github/copilot-ecosystem/issues/1230

## Current state

SDK preview `1.0.12-preview.0` already contains generated `catalog.search` and `mcp.planInstall` types. Stable `1.0.11` does not. Apply remains blocked on runtime implementation.

## Acceptance criteria

- [ ] Code generation consumes an exact verified CLI/platform package version.
- [ ] Node, Python, Go, .NET, Rust, and Java compile with the generated unions.
- [ ] `searchId`, capabilities, handles, and typed authentication failures round-trip without message matching.
- [ ] Search/plan separation and host confirmation requirements are documented.
- [ ] No convenience plan-and-apply wrapper is introduced.
- [ ] Stable release and artefact smoke results are recorded; apply remains explicitly unavailable until regenerated later.