chore(server): add provenance to toolhive-doc-mcp entries (#1226)

Add the sigstore/cosign signing identity block to both the official and
toolhive registry entries for toolhive-doc-mcp. Images were already being
signed keylessly from StacklokLabs/toolhive-doc-mcp release.yml; this just
records the expected identity so the catalog's verifier can check it.

Verified locally with: catalog update-metadata --verify-provenance.

Signed-off-by: Dan Barr <6922515+danbarr@users.noreply.github.com>
Co-authored-by: Dan Barr <6922515+danbarr@users.noreply.github.com>

Author: danbarr

registries/official/servers/toolhive-doc-mcp/server.json

@@ -9,6 +9,13 @@
             "stars": 3
           },
           "overview": "## ToolHive Docs MCP Server\n\nThe toolhive-doc-mcp server allows you to search ToolHive documentation for help with using and contributing to the project (local version). The system maintains a pre-built SQLite vector database containing documentation that undergoes parsing, chunking, and embedding using a local bge-small-en-v1.5 model. When queried, it performs semantic search by comparing queries against stored embeddings to return relevant documentation chunks.",
+          "provenance": {
+            "cert_issuer": "https://token.actions.githubusercontent.com",
+            "repository_uri": "https://github.com/StacklokLabs/toolhive-doc-mcp",
+            "runner_environment": "github-hosted",
+            "signer_identity": "/.github/workflows/release.yml",
+            "sigstore_url": "tuf-repo-cdn.sigstore.dev"
+          },
           "status": "Active",
           "tags": [
             "docs",

registries/toolhive/servers/toolhive-doc-mcp/server.json

@@ -9,6 +9,13 @@
             "stars": 3
           },
           "overview": "## ToolHive Docs MCP Server\n\nThe toolhive-doc-mcp server allows you to search ToolHive documentation for help with using and contributing to the project (local version). The system maintains a pre-built SQLite vector database containing documentation that undergoes parsing, chunking, and embedding using a local bge-small-en-v1.5 model. When queried, it performs semantic search by comparing queries against stored embeddings to return relevant documentation chunks.",
+          "provenance": {
+            "cert_issuer": "https://token.actions.githubusercontent.com",
+            "repository_uri": "https://github.com/StacklokLabs/toolhive-doc-mcp",
+            "runner_environment": "github-hosted",
+            "signer_identity": "/.github/workflows/release.yml",
+            "sigstore_url": "tuf-repo-cdn.sigstore.dev"
+          },
           "status": "Active",
           "tags": [
             "docs",