chore - adopt the loaf.toml envelope for Oven interop after v0.5

[dannymeijer]

Summary

RFC 116 closes its v0.5 declaration and locked-requirement foundation using the current incan.toml [oven.interop] schema. RFC 117 introduces the v0.6 loaf.toml and oven.lock project model. This chore performs that deliberate post-v0.5 envelope transition without reopening RFC 116 C ABI safety semantics or duplicating RFC 116 issue #944 execution and virtual-device evidence.

Scope

• Replace the active project-manifest discovery and serialization path for Oven interop requirements with loaf.toml after the RFC 117 cutover.
• Preserve the existing schema-v1 meaning for declared headers, definitions, target requirements, artifacts, shims, capability constraints, path validation, normalized content identities, and no-ambient-discovery rules while relocating the authored envelope.
• Record the same semantic and physical requirement facts in oven.lock, preserving locked and offline invalidation behavior.
• Update the project-configuration reference, interop tutorials, feature inventory, diagnostics, fixtures, and tests to loaf.toml terminology.
• Reject incan.toml as a legacy compatibility manifest after the cutover, with the targeted diagnostic specified by RFC 117.
• Confirm that C ABI declarations remain source authority; this chore changes project-envelope ownership only.

Explicit boundaries

• Do not alter, delay, or backport the RFC 116 v0.5 release contract.
• Do not redesign C ownership, output, buffer, layout, or verifier semantics from RFC 116.
• Do not duplicate feature - execute Oven interop plans and virtual-device evidence (RFC 116) #944: toolchain and SDK resolution receipts, shim baking, staged Loaf outputs, adapters, and virtual-device evidence remain its v0.6 scope.
• Do not introduce Cargo manifest merging, arbitrary build scripts, or legacy incan.toml parsing.

Done when

• A Loaf project can declare the existing checked-interop requirement contract and Oven records the equivalent normalized facts in oven.lock.
• Existing 0.5 fixtures have Loaf equivalents covering declaration validation, content identity, stale-lock detection, locked/offline behavior, relocation, and diagnostics.
• The user-facing 0.6 documentation describes loaf.toml as the only authored Oven manifest and distinguishes this envelope transition from feature - execute Oven interop plans and virtual-device evidence (RFC 116) #944 target execution.

Relationships

• RFC 116: typed C ABI interop
• RFC 117: loaf.toml and Oven language-neutral project model
• RFC 118: Incan and Oven command-line surfaces
• RFC 116: Typed C ABI interop #939: RFC 116 parent
• feature - govern native artifacts and C/C++ shims through packages (RFC 116) #942: closed v0.5 artifact-requirement foundation
• feature - execute Oven interop plans and virtual-device evidence (RFC 116) #944: v0.6 target-plan execution and virtual-device evidence