[Epic]: Go SDK — make pkg/client/v1 the complete integration surface

[mchmarny]

Goal

Make pkg/client/v1 the complete and defensibly stable integration surface for the core AICR workflow.

An integrator must be able to complete:

snapshot → criteria → recipe → validate → bundle → verify

without importing another AICR pkg/* package.

v1 closure scope

Issue	Required outcome
#2120	Concurrent snapshot collection satisfies the facade's published isolation contract.
#2245	Bundle, validation, and snapshot configuration no longer require Config.Unwrap() or pkg/config.
#2437	The facade derives recipe criteria from a snapshot without exposing pkg/fingerprint or pkg/recipe.
#2028	A merge-blocking architecture test prevents CLI/server business-logic bypasses around the facade.
#2029	The integrator guide and compile-only example demonstrate the complete workflow using only pkg/client/v1.

Acceptance criteria

• The complete workflow compiles using only pkg/client/v1, standard-library packages, and explicitly stable third-party types.
• Snapshot collection is safe for concurrent SDK consumers.
• All configuration needed by the workflow is available through the facade.
• The exported-surface stability test and released-baseline API-diff gate remain green.
• The CLI/server architecture gate rejects new unstable-package bypasses.
• Documentation contains no unstable-package escape hatch for the core workflow.

Post-v1 follow-up

These open native children remain valuable but are not required by the v1 exit gate:

• sdk: expose mirror inventory on the facade; retain trust maintenance in CLI #2025 — mirror inventory.
• sdk: let callers raise the facade verify timeout ceiling #2225 — configurable verification timeout ceiling.
• sdk: validate SigningConfigPath against public-good endpoints #2227 — catalog-signing endpoint validation.
• sdk: CollectSnapshot requires agent fields the CLI defaults #2256 — additional SDK defaults and error-quality hardening.

Native sub-issue inventory

The native graph contains 20 children: 11 closed and 9 open. Five open children are v1 blockers; four are explicitly post-v1.

Out of scope

• Making every CLI capability available through the SDK.
• Publishing trust-cache maintenance before its underlying operation supports reliable cancellation.
• General component upgrade-lifecycle safety.
• Tagging v1.0.0; this epic is a prerequisite, not the release action.