perf: generate only used Platform API operations

[alongubkin]

Summary

• generate the Platform Rust client from the 58 operations used by Alien instead of all 229 operations
• retain transitively reachable components, discriminator mappings, path metadata, and security schemes
• preserve the complete published SDK behind the default full-api feature
• normalize uniquely matching nullable enum copies to named components so Progenitor does not emit duplicate Rust types
• fail generation on missing operations, duplicate operation IDs, unresolved component references, or more than 600,000 filtered generated lines

Impact

• generated Rust: 1,398,184 -> 534,989 lines (-61.7%)
• generated Rust size: about 56 MB -> 22.2 MB (about -60.4%)
• generated structs: 5,533 -> 2,003 (-63.8%)
• generated enums: 3,663 -> 1,372 (-62.5%)
• generated impls: 38,566 -> 14,187 (-63.2%)
• Platform check unit: 326.5s baseline -> 35.4s observed
• Platform build script: 30.1s baseline -> 7.2s observed
• empty-target cargo check -p alien-cli --timings: 7m13s baseline -> 2m34s observed

The timing runs used empty Cargo target directories on the same machine but were recorded under different system load and filesystem-cache conditions. The generated-source reduction is deterministic; timing ratios are observed rather than a perfectly controlled attribution.

Validation

• cargo check -p alien-cli
• cargo test -p alien-platform-api --no-default-features --features rustls
• cargo test -p alien-platform-api
• generated full SDK still exposes all 229 operations
• synthetic coverage for transitive references, cycles, discriminator mappings, path metadata, security schemes, missing/duplicate operations, unresolved references, and nullable enum normalization

Linear: ALIEN-861

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the previously reported missing build module is now included in the published crate.

Findings

1.  Build Module Missing From Package ▶

Fix with agent prompt

### Issue 1
client-sdks/platform/rust/build.rs:3-4
The published crate includes only `build.rs`, `src/**/*`, and `openapi.json`, but this code now unconditionally loads `build/openapi_filter.rs`. Because that module will be missing from the crate archive, builds from crates.io or `cargo package` will fail. Add the new build source to the package include list.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Summary

This PR reduces the generated Rust Platform API client to operations used by Alien while preserving the complete SDK through the default full-api feature.

• Filters the OpenAPI document to required operations and transitively reachable components.
• Preserves path metadata, security schemes, discriminator mappings, and nullable enum compatibility.
• Adds validation for malformed specifications and excessive generated output.
• Includes build/**/* in the published crate, fixing the previously reported packaging failure.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Platform OpenAPI specification] --> B{full-api enabled?}
    B -->|Yes| C[Normalize complete specification]
    B -->|No| D[Retain required operations]
    D --> E[Discover transitively reachable components]
    E --> F[Preserve metadata and security schemes]
    F --> G[Normalize nullable enum copies]
    C --> H[Progenitor]
    G --> H
    H --> I[Generated Rust client]
    I --> J{Filtered output within line limit?}
    J -->|Yes or full-api| K[Compile SDK]
    J -->|No| L[Fail generation]

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_{Reviews (2) · Last reviewed commit: "fix: include Platform API build support ..."}

[alongubkin]

@greptileai The P1 packaging finding is fixed: the crate include list now contains build/**/*, and cargo package -p alien-platform-api --list --allow-dirty confirms build/openapi_filter.rs is present. Please re-review.