feat(generator): SEM003 diagnostic + form-specific relationships (closes #58)

[matt-edmondson]

Summary

Closes #58 — adds the SEM003 diagnostic and the optional forms field on each relationship that the original issue called for. Pairs with the form-coverage matrix doc that landed in #72.

What changed

RelationshipDefinition (in dimensions.json) gets an optional forms array (int[]). When present, the generator only emits operators at those vector forms; when a listed form is missing on a participating dimension, it now surfaces as SEM003 instead of being silently dropped:

warning SEM003: Relationship in dimension 'Force' (crossProducts[Length -> Torque])
explicitly requests form V2, but 'Torque' does not declare that form.
The operator will not be generated.

When forms is omitted, the generator uses per-relationship defaults — preserving every emit decision currently in place:

Relationship	Default forms
integrals, derivatives	[0, 1, 2, 3, 4]
dotProducts	[1, 2, 3, 4] (V0 has no dot product)
crossProducts	[3] (cross product is intrinsically 3D)

Migrated the only current crossProduct (Force × Length → Torque) to "forms": [3] explicitly. The Generated/ tree is unchanged — the migration just makes the V3 expectation visible in metadata.

Verification

• Build clean: dotnet build Semantics.SourceGenerators and dotnet build Semantics.Quantities both succeed with no SEM00x warnings.
• Force3D.Cross(Displacement3D) → Torque3D is still emitted.
• Bogus-form regression check: temporarily setting "forms": [2, 3] on the cross product produces the expected SEM003 against Torque (which has no V2). Reverting to [3] makes the warning go away.

Doc updates

• CLAUDE.md generator diagnostics list adds SEM003 with an example.
• docs/strategy-unified-vector-quantities.md describes the optional forms field.
• AnalyzerReleases.Unshipped.md adds the SEM003 row.

Test plan

• Source-generator build clean
• Quantities build clean (no SEM warnings on current metadata)
• Generated/ tree unchanged vs baseline (default forms for crossProducts matches the existing V3-only emit)
• Manual SEM003 fire test (set forms: [2, 3], observed warning, reverted)
• dotnet test — Semantics.Test cannot restore in this sandbox (Microsoft.NETCore.App.Host.ubuntu.24.04-x64 not in feeds); CI will run.

https://claude.ai/code/session_01Tj63Rddvs9frqLUgsjNEP5

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Generated by Claude Code

[sonarqubecloud]

Quality Gate failed

Failed conditions
1 Security Hotspot
0.0% Coverage on New Code (required ≥ 80%)
C Security Rating on New Code (required ≥ A)
C Reliability Rating on New Code (required ≥ A)

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