feat: expose deployment group external IDs in clients

[alongubkin]

Summary

• regenerate the public Platform OpenAPI schemas for deployment group external IDs
• expose ensure, exact-read, and explicit-update operations in the TypeScript SDK
• verify the build-time generated Rust SDK surface

Platform API: alienplatform/platform#239

Validation

• NODE_OPTIONS=--max-old-space-size=8192 pnpm build in client-sdks/platform/typescript
• cargo test -p alien-platform-api
• cargo test -p alien-platform-api --test deployment_group_external_id

Linear: ALIEN-440

[greptile-apps]

Greptile Summary

The PR exposes deployment-group external IDs across the generated client SDKs.

• Regenerates the Platform OpenAPI schemas with external-ID fields and operations.
• Adds TypeScript ensure, exact-read, and explicit-update methods with required mutation bodies.
• Extends the Rust public-surface test to construct the explicit-update request and operation builder.
• Updates CLI onboarding Git handling to retain the repository handle while reading remote metadata.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
client-sdks/platform/typescript/src/models/operations/ensuredeploymentgroupbyexternalid.ts	The ensure operation now requires its request body in both the TypeScript type and outbound validation schema, resolving the prior bodyless-PUT issue.
client-sdks/platform/typescript/src/models/operations/setdeploymentgroupexternalid.ts	The explicit-update operation requires its body before request encoding, including when clearing the external ID with null.
client-sdks/platform/rust/tests/deployment_group_external_id.rs	The compile-time public-surface test now constructs the explicit-update body and operation builder, resolving the prior coverage finding.
client-sdks/platform/typescript/src/sdk/deploymentgroups.ts	Adds public SDK entry points for ensuring, reading, and updating deployment groups by external ID.
crates/alien-cli/src/git_utils.rs	Refactors repository discovery so the repository remains available while origin metadata is read.

_{Reviews (12): Last reviewed commit: "fix: align external ID client schema wit..." | Re-trigger Greptile}