Bootstrap controller-side dependencies before rig workflow launch

[chubes4]

Problem

The canonical SSI fixture-matrix workflow is conceptually a Homeboy rig operation, but its controller-side launcher failed before Homeboy could orchestrate anything:

Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'pngjs'
imported from .../lib/fixture-matrix/collectors/visual-parity.mjs

Manual recovery required entering the product checkout, identifying its package manager, and running npm ci. Only then could the Homeboy rig install/sync/bench sequence begin.

Homeboy already supports declared dependency materialization for rig workloads (#7888), but the operator entrypoint that selects and launches the rig still depends on an implicitly hydrated controller checkout.

Context: browser verification for Automattic/blocks-engine#659.

Expected behavior

A canonical rig workflow has one Homeboy entrypoint that performs controller and runner dependency readiness from declarations before loading product-owned orchestration modules. Operators do not manually hydrate a checkout to reach Homeboy.

Acceptance criteria

• Rigs can declare controller-side launcher dependencies and expected outputs.
• Homeboy materializes/verifies them before invoking a product-owned launcher.
• A missing dependency produces structured setup evidence and automatic bounded repair.
• The fixture-matrix workflow can start from a clean checkout with no pre-existing node_modules.
• Setup time remains outside measured benchmark timing.

AI assistance

• AI assistance: Yes
• Tool: OpenCode with OpenAI GPT-5.6 Sol
• Used for: Diagnosing the pre-orchestration module failure, applying the manual recovery, and mapping it to Homeboy rig dependency contracts.