Give the quantum factorisation a name that does not collide

[Rafael-SOWNet]

Closes #843, taking option 1 from that issue.

The collision

Two public methods, one letter apart, unrelated operations, identical shapes:

member	operation
Entity.Factorize(int level = 2)	algebraic factoring of an expression
MathS.Quantum.Factorise(Entity)	tensor factorisation of a quantum state

Nothing but the name distinguished them, and the name barely did.

Why not just Factorize

That fixes the spelling and makes the API worse — two public Factorize methods doing unrelated things. MathS.Quantum already holds the inverse operation as TensorExpand, so:

MathS.Quantum.TensorFactorize(state)   // superposition -> tensor product
MathS.Quantum.TensorExpand(state)      // tensor product -> superposition

names the domain and the direction, pairs with its inverse, and ends the collision. The spelling is fixed as a side effect rather than as the point.

One addition beyond the issue

Auditing the recorded public surface while doing this turned up MathS.Quantum.IsNormalised, still British. My claim in #843 that Factorise was the last one was wrong.

It is renamed to IsNormalized here. It carries no collision, only the spelling — but it is public, so 2.0 is equally the last release that can change it, and shipping one British member after two renames made expressly to remove them would be the wrong outcome. Say the word if you would rather it were split out.

The rule I applied to the non-public names

• The internal Factorisation class becomes Factorization and its method follows the public one — it is that member's implementation, so they should not disagree.
• AsymptoticSeries has a private Normalised that is deliberately left alone. Private names carry no deadline; there is no reason for a naming change to reach into the limits code and enlarge the review surface.

AGENTS.md also says "Factorisation into irreducibles is polynomials only" — prose about polynomial factoring, not this member, and correctly untouched.

Measured

The public-surface baseline from #841 makes the blast radius self-reporting. The complete diff of PublicApi.txt for this PR:

-AngouriMath.MathS+Quantum.Factorise(AngouriMath.Entity) : AngouriMath.Entity
-AngouriMath.MathS+Quantum.IsNormalised(AngouriMath.Entity) : System.Nullable<System.Boolean>
+AngouriMath.MathS+Quantum.IsNormalized(AngouriMath.Entity) : System.Nullable<System.Boolean>
+AngouriMath.MathS+Quantum.TensorFactorize(AngouriMath.Entity) : AngouriMath.Entity

Two members out, two in, nothing else moved.

Passed! - Failed: 0, Passed: 6050, Skipped: 14, Total: 6064 - UnitTests.dll (net10.0)

AngouriMath, UnitTests, AngouriMath.FSharp and AngouriMath.CPP.Exporting all build with 0 errors.

After this

The public surface has one spelling throughout, and it is checkable rather than asserted — PublicApi.txt contains no -ise, -ised or -isation member.

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