Build manifest

The source-built JS compiler supports:

sakura build --manifest src

A successful build writes JavaScript to target/sakura/js and the manifest to target/sakura/manifest.json, relative to the working directory. --out-dir changes the JavaScript directory; the manifest path stays target/sakura/manifest.json. A failed build does not write a new manifest, so check the exit status before consuming an existing file.

The manifest is one JSON object with:

• schema_version: "1.0" and the input snapshot hash.
• compiler.version and compiler.git; local builds may have a null git value.
• trusted entries for the compiler, emitted runtime (with SHA-256), std host bindings, user @external declarations, @trust reasons and @total declarations.
• obligations with an ID, symbol ID, clause, status and source span. Current contract records have status runtime_checked.

Obligation IDs use o: followed by a digest of the symbol, clause name and normalized predicate. A function-body edit that preserves these does not change its obligation ID. That identity is not a proof-cache validity guarantee: M4 verification must also track bodies and other dependencies.

This records assumptions and runtime obligations; it does not certify the program. Compile-time literal evaluation already decides some introductions, while sakura verify and proof-driven check removal remain planned M4 integration. See the roadmap.