Update docs, fix marketplace

.claude-plugin/marketplace.json

@@ -1,13 +1,26 @@
 {
+  "$schema": "https://anthropic.com/claude-code/marketplace.schema.json",
+  "name": "virtuslab-cellar",
+  "description": "VirtusLab Cellar marketplace — JVM API lookup tool for Claude Code",
+  "owner": {
+    "name": "VirtusLab",
+    "email": "opensource@virtuslab.com"
+  },
   "plugins": [
     {
       "name": "cellar",
-      "source": "..",
       "description": "Look up the public API of any JVM dependency (Scala 3, Scala 2, Java) from the terminal",
-      "version": "0.1.0",
-      "repository": "https://github.com/virtuslab/cellar",
+      "source": {
+        "source": "github",
+        "repo": "VirtusLab/cellar"
+      },
+      "category": "development",
       "license": "MPL-2.0",
-      "keywords": ["scala", "java", "jvm", "api", "documentation"]
+      "keywords": ["scala", "java", "jvm", "api", "documentation"],
+      "author": {
+        "name": "rochala"
+      },
+      "homepage": "https://github.com/VirtusLab/cellar"
     }
   ]
 }

README.md

@@ -24,7 +24,25 @@ Cellar gives agents — and humans — a single shell command that returns exact
 
 ## Installation
 
-Download the native binary for your platform from https://github.com/simple-scala-tooling/cellar/releases/latest, then extract and install:
+### Nix
+
+Run without installing:
+
+```sh
+nix run github:VirtusLab/cellar -- get-external org.typelevel:cats-core_3:2.10.0 cats.Monad
+```
+
+Install into your profile:
+
+```sh
+nix profile install github:VirtusLab/cellar
+```
+
+A Nix overlay is also available at `github:VirtusLab/cellar#overlays.default`.
+
+### Manual
+
+Download the native binary for your platform from https://github.com/VirtusLab/cellar/releases/latest, then extract and install:
 
 ```sh
 tar xz -f cellar-*.tar.gz
@@ -122,6 +140,54 @@ cellar get-external org.typelevel:cats-core_3:latest cats.Monad
 | `-r`, `--repository <url>` | external commands | Extra Maven repository URL (repeatable) |
 | `-l`, `--limit <N>` | `list`, `search` | Max results (default: 50) |
 
+## Configuration
+
+Cellar loads configuration from HOCON files and environment variables. Files are loaded in order, with later values overriding earlier ones:
+
+1. Built-in defaults
+2. `~/.cellar/cellar.conf` (user-level, optional)
+3. `.cellar/cellar.conf` (project-level, optional)
+
+Use `--config <path>` / `-c <path>` to load a specific file instead.
+
+### Default config
+
+```hocon
+mill {
+  # Binary to invoke when extracting Mill classpaths
+  binary = "./mill"           # env: CELLAR_MILL_BINARY
+}
+
+sbt {
+  # Binary to invoke when extracting sbt classpaths (e.g. "sbt", "sbtn")
+  binary = "sbt"              # env: CELLAR_SBT_BINARY
+  # Extra arguments passed to sbt, space-separated (e.g. "--client")
+  extra-args = ""             # env: CELLAR_SBT_EXTRA_ARGS
+}
+```
+
+### Examples
+
+Use `sbtn` instead of `sbt`:
+
+```hocon
+sbt { binary = "sbtn" }
+```
+
+Use sbt in `--client` mode:
+
+```hocon
+sbt { extra-args = "--client" }
+```
+
+Use a custom Mill wrapper:
+
+```hocon
+mill { binary = "./millw" }
+```
+
+Or via environment: `CELLAR_SBT_BINARY=sbtn cellar get --module core cats.Monad`
+
 ## Output conventions
 
 - **stdout** — Markdown content (signatures, docs, source)
@@ -257,6 +323,12 @@ java -jar out/cli/assembly.dest/out.jar get-external org.typelevel:cats-core_3:2
 ./mill lib.test
 ```
 
+### Installing a local build with Nix
+
+```sh
+./mill cli.nativeImage && nix profile install --impure .#dev
+```
+
 ## Tech stack
 
 Scala 3, Cats Effect, fs2, [tasty-query](https://github.com/scalacenter/tasty-query), [Coursier](https://get-coursier.io/), [decline](https://ben.kirw.in/decline/), Mill.