Follow OverPy argument shifting for omitted defaulted middle arguments

[e54-bot]

Goal

Match the pinned OverPy 9.7.10 argument-shifting behavior when a defaulted middle argument is omitted for createBeam, getPlayersInRadius, createHomingProjectile, and createProjectileEffect.

Context

The pinned reference shifts remaining arguments left without type checking and can therefore emit a structurally mistyped Workshop call. opy-rs currently rejects these forms instead of reproducing that output.

The current difference has two owners:

• OPY argument binding: opy-rs must implement the reference's omitted-middle-argument shift.
• Canonical Workshop validation: the shifted calls currently fail canonical semantic validation. Any allowance must be defined by workshop-rs narrowly enough that normal validation is not weakened globally.

Until both sides are resolved, the behavior remains an explicit compatibility exception rather than a hidden workaround.

Scope

• Establish the required workshop-rs contract for admitting exactly the reference-shaped shifted calls without disabling canonical validation for unrelated programs.
• Change the opy-rs binder to shift omitted defaulted middle arguments for the four functions.
• Remove the corresponding compatibility exception from docs/architecture/language-core.md and tools/overpy/probe-gaps.json.
• Update focused tests to require the pinned reference structure.

Non-goals

• Weakening canonical validation globally.
• Skipping Workshop validation in opy-rs.
• Adding per-function validation bypasses owned only by the OPY compiler when the underlying Workshop contract belongs in workshop-rs.
• Adding or renaming Workshop catalog entries.

Acceptance criteria

• The four functions compile omitted-middle-argument calls with Workshop structure equal to the pinned OverPy reference.
• probe-gaps.json no longer lists reference-binds-mistyped-optional.
• The approved exception in language-core.md is removed or superseded by the implemented contract.
• Canonical validation remains effective for unrelated invalid programs.
• Standard repository gates and the builtin compatibility probe pass.

Dependencies / ownership

• opy-rs: OverPy argument binding and compatibility tests.
• workshop-rs: canonical validation contract required to represent the shifted reference output safely.