fix(web): reduce build memory usage and update OMA

[gracefullight]

Next.js builds previously compiled and generated pages in one process without an explicit worker limit. Limit workers to three, disable the Turbopack build filesystem cache, and run compile followed by generate in separate processes. Docker builds use the same script and stop if either phase fails.

Update managed OMA skills, workflows, hooks, and vendor adapters to 15.0.17 using oma update. Include the existing Serena Dart language server settings and YAML formatting changes.

Validation:

• Web typecheck and Biome checks passed; wrapped Next config preserves the memory settings and Serwist integration.
• Dockerfile lint, commit hooks, and push hook passed.
• Changed JSON files and shell scripts passed syntax checks.
• Web Vitest found no test files. API, worker, and mobile gates reused their existing passing results because their inputs were unchanged.
• OMA diagnostics found all installed skills complete and hook wrappers valid; overall diagnostics still reports eight local environment issues.

A production build and an 8 GB memory measurement have not been run. The split build modes are experimental.

[github-actions]

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