Add Microsandbox sandbox blueprint

[Hor1zonZzz]

Summary

Add Microsandbox as a supported sandbox provider blueprint (flue add sandbox microsandbox), following the same format as the existing sandbox blueprints (Daytona, E2B, boxd, Mirage, ...).

Why

Microsandbox boots real hardware-isolated microVMs (a guest kernel, not container namespaces) from any OCI image via a self-hosted TypeScript SDK with no API key and no server to run — the microsandbox npm package embeds the runtime through a native addon. That's a meaningfully different tradeoff from the existing hosted sandbox providers (Daytona, E2B, Modal): no account, no network dependency, fully local/self-hosted, sub-second boot.

What this adds

• blueprints/sandbox--microsandbox.md — the SandboxApi adapter implementation guide, in the same format as the other sandbox blueprints
• apps/ecosystem-catalog.ts / apps/docs/src/lib/docs-navigation.ts / apps/docs/src/content/docs/ecosystem/sandboxes/microsandbox.md — ecosystem listing + docs page
• Regenerated skills/flue/SKILL.md docs catalog

Implementation notes

The SandboxApi implementation was checked against the actual sdk/node-ts source in superradcompany/microsandbox (not just its docs), so a few details are worth calling out:

• Filesystem ops map directly onto sandbox.fs() — read()/write() already accept/return Uint8Array | string, so no buffer conversion is needed, unlike Daytona/E2B.
• mkdir/rm only support single-level operations, so recursive mkdir falls back to a shell command and rm rejects unsupported recursive/force with SandboxOperationUnsupportedError, matching the contract.
• exec() runs through sh -c '<command>' via execStreamWith(), so cwd/env/timeoutMs all forward through the native ExecOptionsBuilder — timeoutMs maps directly to .timeout(ms) with no unit conversion needed. AbortSignal gets true mid-flight cancellation via the streaming handle's kill(), not a Promise.race fake.
• A native ExecTimeoutError is converted to an exit-code-124 result, matching the convention documented for other adapters.

Testing

• pnpm --dir packages/cli run prebuild regenerates the blueprint index cleanly (39 blueprints)
• Ran the docs website locally and verified flue add sandbox microsandbox, the msb alias, and flue update sandbox microsandbox all return the expected guide via FLUE_REGISTRY_URL pointed at the local server
• pnpm --dir apps/docs run check:types (astro check): 0 errors
• packages/cli test suite: 93/93 node --test + 83/83 vitest passing, including the SKILL.md catalog sync test
• biome check / prettier clean on all touched files

🤖 Generated with Claude Code

[astrobot-houston]

Thanks for the contribution! We're closing this PR and moving the conversation to the existing thread: #417

We've moved to a model where bugs and feature proposals are discussed in issues/discussions before code review, so the community can help prioritize and shape the work. Your branch is linked from the new thread so the implementation isn't lost — please join us there to continue the conversation.

— astrobot 🤖