[softmarshmallow]

N3's executable documentation harness currently owns document composition and publication inside its application replay. This extracts a reusable Rust SDK and keeps N3's existing published guide byte-for-byte compatible.

Changes

• Add the unpublished executable-docs SDK for Rust-authored prose, checked observations, frozen resources, typed references, and contributor notes. Reader and Contributor exports reuse one execution.
• Let adopters configure page/resource paths, baseline roots, audience directories, and relative-path resolution, or integrate directly with their own tests and CLI. No repository discovery or prescribed project topology is required.
• Share strict artifact ownership, comparison, staged publication, and recovery with N3. Preserve audience isolation, portable inventory paths, and separation from reserved transaction directories.
• Migrate the hand-tool and navigation narratives into their Rust scenarios while retaining production replay, exact media, and the existing N3 manifest. The remaining 26 guides keep their templates.
• Add CLI, serde_json, and configured-layout examples, behavioral regressions, API documentation, an architecture contract, and native/CI verification gates.

Validation

• Clean-commit native just verify through the pre-push hook: formatting, workspace Clippy, tooling, SDK/consumer tests, doctests, strict API docs, N3 tests with exact guide replay, and measurement checks.
• Final standalone Rust 1.95 copy: 113 SDK tests and four doctests passed. A project with no root Cargo manifest or Git repository produced identical exports after relocation and invocation from unrelated working directories.
• Final cached pinned Linux environment: 125 SDK/consumer tests and four doctests passed, including case-sensitive filesystem behavior.
• All 138 existing N3 guide and renderer-baseline files remain unchanged.

The SDK/API and manifest remain experimental and unpublished. Markdown is the current complete exporter; independent developer adoption, alternate publishers, and Git/diff views remain future work. Windows inventory separators are corrected, but Windows runtime validation has not been performed.