Add probe tools to hal0-admin MCP: gpu_target_version, npu_status, env_report, model_store_probe

[thinmintdev]

What to build

Add four read-only host-introspection tools to the hal0-admin MCP server. These centralise probing logic currently scattered (or absent) and unblock several downstream consumers: Hermes bootstrap env_probe phase, the dashboard's host panel, and future support-bundle exporters.

The tools mirror recipes already documented in docs/internal/hermes-env-probe-recipes-2026-05-23.md. They're explicitly LXC-aware: don't read /lib/firmware/amdnpu/ or modinfo amdxdna (both fail inside our LXC); use lsmod, /dev/accel/accel0, and PCI sysfs instead.

Tools:

• gpu_target_version() → returns KFD gfx_target_version (e.g., "gfx1151" for Strix Halo).
• npu_status() → {present, device_node, driver_loaded, pci_id}.
• env_report() → consolidated host snapshot (container type, CPU, RAM, GPU, NPU, network basics).
• model_store_probe(path) → {fstype, free_mb, total_mb, writable, is_uma_aware}.

All four classify as "autonomous read" per ADR-0004's MCP gating model.

Acceptance criteria

• Four tools added to src/hal0/mcp/admin.py and registered in the FastMCP server build.
• Each tool has a unit test in tests/mcp/test_admin.py verifying schema + happy path.
• env_report() returns a dataclass with all fields documented in the env-probe recipes doc.
• LXC-correct: tools don't fail inside our hal0 LXC because of host-only kernel files.
• gpu_target_version() returns "gfx1151" on the hal0 LXC (Strix Halo).
• Tools surface in tools/list MCP response.

Blocked by

None — can start immediately.

References

• docs/internal/hermes-env-probe-recipes-2026-05-23.md
• docs/internal/hermes-bootstrap-plan-2026-05-23.md §6 (consumer context)
• ADR-0004 (admin MCP gating model)