dev-tools: give every node the toolchains to build and test the mesh's code (issue 626)

Every node is a development machine: an agent builds a change and runs its tests there before opening a pull request, and the lab tests it afterwards as QA. No module declared Go or npm, so no node could do the first part.

modules/dev-tools/README.md

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+# dev-tools
+
+The tools a machine needs to develop the mesh's own code (novox/hq issue 626). Every node is a development
+machine: an agent working on a change builds it and runs its tests there, with these tools, before it opens a
+pull request. The lab is the QA step after that: it tests the work in a sandbox, through its seat at the mesh
+scope, and is not where development happens.
+
+Assign it to every node.
+
+## Owns
+
+| what | package | class (ADR 0182) |
+|---|---|---|
+| the Go toolchain, for `go build` and `go test` in every Go module | `go` | package |
+| a C compiler, for `go test -race` and cgo | `gcc` | package |
+| make | `make` | package |
+| Node.js and npm, for the TypeScript modules' `npm ci` and `npm test` | `nodejs`, `npm` | package |
+| Python, for the scripts some checks run | `python` | package |
+| git and jq | `git`, `jq` | package |
+
+All are in the distribution's official repositories, so the node-engine's package manager installs them on any
+node. The versions are the distribution's: the toolchain images that run `mesh/repo-check` stay the judge of a
+pull request, and a local run is the developer's early answer, not the verdict.
+
+Nothing else is placed: no file, no service, no environment. A module's own dependencies come from its lock
+file (`go.mod`, `package-lock.json`), as in the toolchain images.

modules/dev-tools/module.json

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+{
+  "module": "dev-tools",
+  "version": "1",
+  "capabilities": [
+    "package-manager"
+  ],
+  "resources": [
+    {
+      "id": "go",
+      "type": "package",
+      "package": "go"
+    },
+    {
+      "id": "c-compiler",
+      "type": "package",
+      "package": "gcc"
+    },
+    {
+      "id": "make",
+      "type": "package",
+      "package": "make"
+    },
+    {
+      "id": "nodejs",
+      "type": "package",
+      "package": "nodejs"
+    },
+    {
+      "id": "npm",
+      "type": "package",
+      "package": "npm"
+    },
+    {
+      "id": "python",
+      "type": "package",
+      "package": "python"
+    },
+    {
+      "id": "git",
+      "type": "package",
+      "package": "git"
+    },
+    {
+      "id": "jq",
+      "type": "package",
+      "package": "jq"
+    }
+  ]
+}