Add marketplace command (#17087)

Added a new top-level `codex marketplace add` command for installing
plugin marketplaces into Codex’s local marketplace cache.

This change adds source parsing for local directories, GitHub shorthand,
and git URLs, supports optional `--ref` and git-only `--sparse` checkout
paths, stages the source in a temp directory, validates the marketplace
manifest, and installs it under
`$CODEX_HOME/marketplaces/<marketplace-name>`

Included tests cover local install behavior in the CLI and marketplace
discovery from installed roots in core. Scoped formatting and fix passes
were run, and targeted CLI/core tests passed.

codex-rs/core/config.schema.json

@@ -764,6 +764,50 @@
         }
       ]
     },
+    "MarketplaceConfig": {
+      "additionalProperties": false,
+      "properties": {
+        "last_updated": {
+          "default": null,
+          "description": "Last time Codex successfully added or refreshed this marketplace.",
+          "type": "string"
+        },
+        "ref": {
+          "default": null,
+          "description": "Git ref to check out when `source_type` is `git`.",
+          "type": "string"
+        },
+        "source": {
+          "default": null,
+          "description": "Source location used when the marketplace was added.",
+          "type": "string"
+        },
+        "source_type": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/MarketplaceSourceType"
+            }
+          ],
+          "default": null,
+          "description": "Source kind used to install this marketplace."
+        },
+        "sparse_paths": {
+          "default": null,
+          "description": "Sparse checkout paths used when `source_type` is `git`.",
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        }
+      },
+      "type": "object"
+    },
+    "MarketplaceSourceType": {
+      "enum": [
+        "git"
+      ],
+      "type": "string"
+    },
     "McpServerToolConfig": {
       "additionalProperties": false,
       "description": "Per-tool approval settings for a single MCP server tool.",
@@ -2414,6 +2458,14 @@
       ],
       "description": "Directory where Codex writes log files, for example `codex-tui.log`. Defaults to `$CODEX_HOME/log`."
     },
+    "marketplaces": {
+      "additionalProperties": {
+        "$ref": "#/definitions/MarketplaceConfig"
+      },
+      "default": {},
+      "description": "User-level marketplace entries keyed by marketplace name.",
+      "type": "object"
+    },
     "mcp_oauth_callback_port": {
       "description": "Optional fixed port for the local HTTP callback server used during MCP OAuth login. When unset, Codex will bind to an ephemeral port chosen by the OS.",
       "format": "uint16",