feat(runtime): add environment provider adapters

[drewstone]

Summary

• import the shared environment-provider contract from @tangle-network/agent-interface@0.14.0
• add runtime adapters between AgentEnvironmentProvider, SandboxClient, and ExecutorFactory
• add named provider registry support through createExecutor({ backend: 'provider' })
• add the environment provider spec and refresh generated API docs

Verification

• pnpm run typecheck
• pnpm test src/runtime/environment-provider.test.ts
• pnpm run build
• env -u INTELLIGENCE_OTLP_ENDPOINT -u OTEL_EXPORTER_OTLP_ENDPOINT pnpm test
• pnpm run docs:api
• pnpm run docs:freshness
• git diff --check

[tangletools]

✅ Auto-approved PR — 7b40963b

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_{tangletools · auto-approval · reason: blanket_auto_approve · 2026-06-26T19:29:28Z}

[tangletools]

✅ Auto-approved PR — 44ed090a

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_{tangletools · auto-approval · reason: blanket_auto_approve · 2026-06-26T19:35:51Z}

[tangletools]

✅ Auto-approved PR — fc773495

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_{tangletools · auto-approval · reason: blanket_auto_approve · 2026-06-26T19:41:09Z}