Split SimpleAPI.lean across package boundaries

[aqjune-aws]

Prepare for the repository split by aligning API boundaries with package boundaries. Each future package (StrataDDM, Strata, StrataPython, etc.) will expose only the API surface it owns, without requiring downstream packages to import the full SimpleAPI and its dependencies.

SimpleAPI.lean is now a thin re-export of the modules in:

• Strata/DDM.lean
• Strata/Languages/Core/Core.lean
• Strata/Languages/Laurel/Laurel.lean
• Strata/Languages/Python/Python.lean

Additional changes:

• New LaurelAST.lean: Laurel AST types extracted from Laurel.lean so downstream files that needs only the AST (e.g., PythonLaurelTypedExpr.lean) can avoid pulling in the full Laurel API.
• Core.runTransforms extracted to PipelinePhase.lean — the inline transform loop from Verifier.lean is now a standalone function on List PipelinePhase, with optional telemetry and debug-file output.
• Core.TransformPass inductive removed — replaced by Core.PipelinePhase values via open pass* constructors.
• readStrataProgram in StrataMainLib now delegates to Strata.readStrataText (DDM) instead of manually assembling dialect contexts.
• coreToGeneric (noncomputable opaque) → coreToStrataProgram — now implemented via CST round-trip.

[aqjune-aws]

Quite close to the final version - the types in APIs can be regarded as opaque types because APIs will provide the 'creators' of them. For example, users won't have to know what is the definition of Factory because Core.defaultFactory will return the default Factory. If they want more fine-grained control over this type, they can actually start to depend on the definition of Factory at the cost of being sensitive to the version of commit of Strata.

[joehendrix]

I think Strata/Languages/Core/Core.lean should be renamed to Strata/Languages/Core.lean or justStrata/Core.lean given its prominance. I do wonder whether the transforms in Strata.Transform should be moved under the Core namespace as well. Are they all Core to Core transforms?

[aqjune-aws]

I do wonder whether the transforms in Strata.Transform should be moved under the Core namespace as well. Are they all Core to Core transforms?

Some of the transformations are on pure Imperative programs (e.g., StructuredToUnstructured). This was under a design assumption that other languages will have been written using Imperative and Lambda. It's hard to decide whether Strata.Transform should be moved to Strata.Languages.Core.Transform or not. :/

[shigoel]

I do wonder whether the transforms in Strata.Transform should be moved under the Core namespace as well. Are they all Core to Core transforms?

Most of them are, but there are some transforms that should be moved under DL (e.g., StructuredToUnstructured). I think we should find appropriate homes for them and this can be done in this PR or in the one that creates the StrataCLI package.

[atomb]

Just one key change to request: I'd like to avoid module names with duplication. I'd prefer Strata.Languages.Core.Core to be just Strata.Languages.Core

[aqjune-aws]

Let me fix the conflicts after recent updates..!