Integrate Loom dependency

[avrabe]

Goal

Configure Synth to depend on Loom repository.

Tasks

• Add Loom as git dependency in MODULE.bazel
• Import Loom ISLE rules
• Import Loom optimization passes
• Verify Synth can use Loom components
• Document integration
• Add tests using Loom components

Loom Repository

• URL: https://github.com/pulseengine/loom
• Components: ISLE rules, optimization passes

Acceptance Criteria

• ✅ Loom dependency resolves correctly
• ✅ Synth can use Loom optimization rules
• ✅ Build remains hermetic
• ✅ Tests pass with Loom integration

[avrabe]

Triage Update: Not Started

No Loom dependency exists in either Cargo.toml or MODULE.bazel. The Loom repository exists at https://github.com/pulseengine/loom but is not yet integrated.

Context from #34

Per the Meld Platform architecture (issue #34), the pipeline is:

Components → Meld (fuse) → Loom (optimize) → Synth (compile to ARM)

Loom operates upstream of Synth — it optimizes WASM before Synth sees it. Integration options:

1. Build-time CLI dependency: synth compile --optimize shells out to loom optimize first
2. Bazel dependency: Add Loom as bazel_dep in MODULE.bazel for the Bazel pipeline
3. Library dependency: Import Loom's optimization passes as a Cargo dependency

The simplest path is option 1 (CLI orchestration) or handling Loom externally in the build pipeline, since Loom's output is standard WASM that Synth already accepts.