v0.3.0 - Hardware dashboard + knob context + Explain context + Open WebUI link

Hardware dashboard:
- New hardware.py module: SSH probes each Spark for hostname, uptime, load+cores, RAM, disk, GPU (name, util, temp, power) + per-process GPU memory sum
- DGX Spark uses unified memory (nvidia-smi memory.total returns N/A); fall back to per-process compute memory and compute fraction against system RAM. Marks with gpu_unified_memory=true.
- 4s TTL cache in HardwareProbe to avoid hammering
- /api/hardware returns per-Spark snapshot
- UI: 'Spark hardware' section at the top with per-Spark cards (CPU load, RAM, GPU mem (unified), GPU util + temp + power, disk) — bars with warn threshold styling
- Polls every 8s

Knob context (tied to live hardware):
- Each Advanced knob now shows plain-English help text
- 'GPU memory %' shows '~N GB allocated · ~M GB left for OS/buffers' computed from actual Spark RAM
- 'Max context' shows '~N pages of text'
- Toggles show tradeoff descriptions

Explain context:
- '✨ Explain context' button on the update banner
- /api/explain-updates POST: forwards pending commits to the loaded vLLM model and streams its response back as SSE
- Renders into an expandable 'Explained by the loaded LLM' section under Pending commits
- Reasoning tokens shown italicized when the model emits them

Open WebUI integration:
- New 'Open WebUI URL' optional field in Configure Sparks
- /api/config exposes it; UI shows 'Open chat ↗' button in the top bar if set

Downloads:
- Third radio option: Spark 1 only / Spark 2 only / Both Sparks
- Backend picks SSH target based on mode
- HF repo link icon next to the input
- Helper line about NVFP4 for Blackwell

Model cards:
- Repo name is now a clickable link to its Hugging Face page

Package: bump 0.3.0:0

package/startos/main.ts

@@ -19,6 +19,7 @@ export const main = sdk.setupMain(async ({ effects }) => {
     magpie_host: '',
     magpie_user: '',
     magpie_container: '',
+    open_webui_url: '',
   }
 
   return sdk.Daemons.of(effects).addDaemon('primary', {
@@ -47,6 +48,7 @@ export const main = sdk.setupMain(async ({ effects }) => {
         MAGPIE_USER: cfg.magpie_user,
         MAGPIE_CONTAINER: cfg.magpie_container,
         MODELS_OVERRIDES: '/data/models-overrides.yaml',
+        OPEN_WEBUI_URL: cfg.open_webui_url,
         BIND_PORT: String(uiPort),
       },
     },