feat: lift angular momentum to Hilbert space

[lizr-phys]

Lift the existing Schwartz-space angular momentum components L_ij = x_i p_j - x_j p_i to partially defined linear operators on SpaceDHilbertSpace d, with domain SchwartzSubmodule d.

The construction transports the existing operator 𝐋 i j through schwartzEquiv volume and schwartzIncl volume, preserving the current Schwartz-space API.

This PR adds application and almost-everywhere bridge lemmas, proves that the operator preserves the Schwartz submodule and has dense domain, and establishes symmetry and the corresponding Physlib IsUnbounded result. The symmetry proof uses the canonical commutation relation together with the existing position and momentum inner-product identities.

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[jstoobysmith]

I think I would put all of these results under angularMomentumOperator if possible, and in that file not in Commutation

[lizr-phys]

Thanks! I’ve updated this accordingly — the angular-momentum-specific results are now organized around angularMomentumOperator and moved into AngularMomentum.lean.

[jstoobysmith]

There is also a merge conflict on this PR

awaiting-author

[jstoobysmith]

I've approved this. This looks good to me. Many thanks. Assuming it passes the linters, I will merge shortly.