Revert "TileOP: enforce CUBE InternalAcc CCTRL legality (spec#236) (#84)"

[VV0003]

Reverts the CUBE InternalAcc CCTRL legality change (#84) from linx.

Reason

Version tag freeze: a release tag is being cut from linx and this feature is not in scope for that version. This is a timing revert, not a quality revert — no defects were identified in #84.

The change should be re-landed after the tag is cut. The branch codex/cube-internalacc-legality (commit de84656) remains intact for that.

What this reverts

• Validator wiring (validate_cube_ctrl_contract call sites in matmul/matmul_acc/matmul_bias/matmul_mx/MX-5SRC)
• MX/IsAccForm template-argument mispositioning fixes (12 call sites)
• Chainable with_cube_ctrl fix
• CubeInternalAcc golden/negative fixtures

Not touched (predate #84, from 33cb600): typed CubeControl enum, Options::raw_acc()/acc_hint(), PTO_MATMUL_HEADER CCTRL encoding, C,A,B operand order.

Verification

• Restores linx to exactly the pre-TileOP: enforce CUBE InternalAcc CCTRL legality (spec#236, Phase 1) #84 content (git diff vs 80cfeac is empty)
• Post-revert: unittest 40/40; SharedMatmul/GroupMatmul/TMatmulAcc*/PostProcessCombos/TGEMV* fixtures all compile clean

Note for re-landing

The latent bugs #84 fixed become active again after this revert (inert CCTRL[1] check on non-ACC paths, MX mispositioning on two ACC emitters, attribute-dropping static with_cube_ctrl). They are documented in #84 and should be re-landed together with the feature after the tag.