Replace build-script path sharing with a stable build-support boundary (#49)

[leynos]

Summary

This branch replaces #[path] source sharing between the root build script and library tests with the workspace-internal theoremc-build-support crate. It gives build discovery, suite generation, and generated Cargo metadata a stable Cargo dependency boundary without expanding the public theoremc API.

Closes #49.

Review walkthrough

• Start with the build-support crate and its build preparation adapter, which now own discovery, suite generation, and typed build results.
• Then review the root build-script adapter, which only emits Cargo protocol metadata from the stable internal result.
• Finish with the fixture-crate helper and maintainer guidance, which exercise and document the dependency boundary.

Validation

• make check-fmt: passed.
• make typecheck: passed.
• make lint: passed.
• make test: passed (647/647 nextest tests and doctests).
• make markdownlint: passed.
• make nixie: passed.
• coderabbit review --agent: completed with 0 findings.

References

• Issue #49
• Lody session

Summary by Sourcery

Replace path-based build-script source sharing with a stable internal build-support crate for theorem build integration.

Enhancements:

• Introduce the internal theoremc-build-support crate as a stable Cargo boundary for theorem discovery, suite generation, and build metadata.
• Reduce the root build script to a thin adapter that emits Cargo configuration and rerun metadata without expanding the public theoremc API.
• Update fixture-based behavioral tests to exercise build support through a path dependency rather than copied source modules.

Build:

• Move build-time discovery and suite-generation dependencies into the new workspace build-support crate and register it as the root build dependency.

Documentation:

• Document the build-support crate boundary and updated contribution guidance for build-time functionality.

Tests:

• Keep build discovery and suite-generation unit tests with the build-support crate and adapt Cargo fixture tests to validate the dependency boundary.

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[sourcery-ai]

Reviewer's Guide

Replaces fragile source-file sharing between the root build script and tests with the workspace-internal theoremc-build-support crate, centralizing discovery, suite generation, and typed build results while keeping build.rs as a minimal Cargo-protocol adapter and updating fixture coverage and developer documentation.

Sequence diagram for build-script preparation through Cargo metadata

sequenceDiagram
    participant Cargo
    participant BuildScript as RootBuildScript
    participant Support as TheoremcBuildSupport
    participant Filesystem

    Cargo->>BuildScript: provide CARGO_MANIFEST_DIR and OUT_DIR
    BuildScript->>Support: prepare_build_script()
    Support->>Support: discover_theorem_inputs(manifest_dir)
    Support->>Filesystem: write_theorem_suite(out_dir, discovery)
    Filesystem-->>Support: generated suite written
    Support-->>BuildScript: BuildScriptOutput
    BuildScript->>Cargo: emit theoremc_has_theorems when has_theorems()
    BuildScript->>Cargo: emit rerun_paths()

Loading

File-Level Changes

Change	Details	Files
Introduces a workspace-internal build-support crate that owns theorem discovery, suite generation, and typed build-script orchestration.	Moves discovery and suite modules into the new crate and makes their integration API public within that boundary. Adds BuildScriptOutput and structured BuildScriptError handling for Cargo environment, filesystem, discovery, and generation failures. Preserves deterministic theorem ordering, generated output behavior, and Cargo rerun metadata.	Cargo.toml Cargo.lock crates/theoremc-build-support/Cargo.toml crates/theoremc-build-support/src/lib.rs crates/theoremc-build-support/src/build_script.rs crates/theoremc-build-support/src/discovery.rs crates/theoremc-build-support/src/suite.rs
Reduces the root build script to a thin adapter over the stable build-support dependency boundary.	Replaces #[path] module inclusion and direct dependency usage with prepare_build_script(). Emits the theorem cfg flag and rerun directives from the typed build result. Removes test-only build-support modules from the root library.	build.rs src/lib.rs
Updates behavioral fixtures and tests to exercise build support through a Cargo path dependency rather than copied source sharing.	Copies the build-support crate structure into temporary fixture crates. Changes fixture manifests to depend on theoremc-build-support instead of duplicating its transitive dependencies. Retains coverage for rerun behavior, empty and populated theorem trees, deterministic generation, and path normalization.	tests/common/fixture_crate.rs tests/build_discovery_bdd.rs tests/build_suite_bdd.rs tests/theorem_file_macro_bdd/fixture_crate.rs
Documents the new internal build-support architecture and maintenance workflow.	Revises the build-script walkthrough and layer table to identify the new crate. Explicitly prohibits #[path] sharing and specifies normal dependency-based integration. Adds guidance for extending build-time discovery or generation with unit and Cargo behavioral tests.	docs/developers-guide.md

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#49	Replace build.rs and root-test source sharing via #[path] with a stable internal build-support crate or equivalent boundary for theorem discovery and suite generation.	✅
#49	Update build scripts and behavioral/root tests to consume and validate the new build-support boundary while preserving discovery, suite generation, Cargo rerun metadata, and generated wiring behavior.	✅
#49	Update maintainer documentation to describe the new build-support ownership boundary and reuse policy.	✅

Possibly linked issues

• Replace build-script path sharing with a stable build support boundary #49: The PR replaces #[path] sharing with theoremc-build-support, updates tests and documentation, and preserves build behavior.

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