fix(hal): add tanh + integer clamp to SPIR-V interpreter

[amery]

Summary

The software SPIR-V interpreter's GLSL.std.450 dispatch was missing two
common math builtins. Unknown ext-inst opcodes fall through to
return ValUint(0), so shaders calling these got silently wrong
results (zeros) rather than an error:

• tanh() — Tanh (21) absent (all hyperbolics, 19–24, were missing)
• integer clamp() — SClamp (45) and UClamp (44) absent; only the
  float FClamp (43) was handled

Changes

• Implement Sinh/Cosh/Tanh/Asinh/Acosh/Atanh (19–24) and
  UClamp/SClamp (44–45) in hal/software/shader/glsl_ext.go.
• Add glslTernaryUint / glslTernaryInt helpers, mirroring the
  existing glslBinary* ones.
• Interpreter tests for each: hyperbolic rows in TestGLSLUnaryIntrinsics,
  plus TestGLSLSClamp / TestGLSLUClamp.

Testing

go test ./hal/software/shader/ and go vet ./hal/software/shader/ pass.

Discovery

Surfaced by the born ML framework's webgpu backend on the software path,
where its Tanh and Int32 Clamp ops returned all-zeros. With these
opcodes implemented, both produce correct results.

No existing issue tracked this; still reproducible on main.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[kolkov]

LGTM! Clean implementation, follows all existing patterns.

Verified:

• All 8 opcode numbers correct per GLSL.std.450 spec (Sinh=19–Atanh=24, UClamp=44, SClamp=45)
• Hyperbolic ops use glslUnaryFloat — consistent with Sin/Cos/Tan pattern
• Integer clamp ops use new glslTernaryUint/glslTernaryInt helpers — mirrors existing glslBinary* style
• Tests cover all branches: saturation boundaries (tanh ±10), domain boundaries (acosh(1)), negative range (SClamp)
• float32↔float64 conversion chain matches every other float op in the file

One systemic note (not blocking this PR): unknown GLSL.std.450 opcodes silently return ValUint(0) — this is how Born ML got zeros in the first place. Filed internally as BUG-SW-009 to add a warning log for unimplemented opcodes.

Thanks @amery — shipping in v0.30.3.