Add Workshop-to-DEL decompilation and close remaining declared compatibility gaps

[Teakowa]

Parent: #1

Goal

Add Workshop -> DEL reconstruction after the canonical Workshop representation and forward compiler integration are stable, then close the remaining evidence-backed compatibility gaps in the declared del-rs surface.

Scope

• Define the useful Workshop -> DEL reconstruction contract against canonical workshop-rs semantics.
• Reconstruct valid, useful DEL/OSTW source structures from canonical Workshop semantics without promising recovery of information that Workshop has already erased.
• Prefer semantic equivalence and readable/useful structure over reproducing the upstream decompiler's exact formatting or reconstruction choices.
• Preserve canonical/source provenance where available and document unavoidable information loss such as original comments, formatting, macro structure, source abstractions, local naming, or compiler-generated structure.
• Inventory and implement remaining compiler utilities that Establish the OSTW/DeltinScript feature inventory and compatibility corpus #2 classifies as part of the declared compatibility contract, such as import formats, bundled modules, pathmap-related compiler surfaces, or lobby/project utilities where evidence justifies inclusion.
• Add round-trip and differential evidence appropriate to each supported reconstruction/utility feature.

Non-goals

• Reproducing the VS Code extension, editor commands, Workshop log UI, or upstream debugger UI.
• Claiming exact recovery of original high-level source from raw Workshop.
• Matching upstream decompiler text/formatting when semantic structure is equivalent.
• Treating legacy or editor-only utilities as mandatory without evidence from Establish the OSTW/DeltinScript feature inventory and compatibility corpus #2.

Acceptance criteria

• Supported canonical Workshop programs can be reconstructed into valid DEL/OSTW source within a documented semantic-equivalence contract.
• Round-trip tests distinguish semantic preservation from source preservation and explicitly cover known information-loss boundaries.
• Remaining declared compiler-utility compatibility items have evidence-backed supported/unsupported status.
• No decompiler logic bypasses workshop-rs canonical ownership by maintaining a second raw Workshop parser/catalog in del-rs.
• The compatibility matrix can state the final declared coverage with explicit known limitations rather than a vague percentage claim.

Dependencies

• Integrate DEL lowering and runtime compatibility with workshop-rs #8 forward compiler/runtime integration must be stable enough to validate round trips.
• Depends on a stable canonical Workshop representation from wrightkit/workshop-rs.

Planning notes

Do not pre-split detailed decompiler internals now. Refine this issue only after forward integration and real corpus evidence reveal which reconstruction heuristics and utility surfaces are valuable.