feat(mcp): add Blender to the MCP catalog with a curated 4-tool default

Adds optional-mcps/blender (ahujasid/blender-mcp, stdio via uvx). The
server advertises 22 tools; 18 front optional asset services with no
upstream trim mechanism, so tools.default_enabled pins the install to
the core surface (scene/object info, viewport screenshot, code exec)
and the rest stay opt-in through 'hermes mcp configure blender'.

Manifests can now declare transport.env (static, non-secret subprocess
env vars), parsed/validated in _parse_manifest and written by
_build_server_config — used here to ship DISABLE_TELEMETRY=true per
the no-telemetry-without-opt-in policy. Runtime already honored
per-server env; manifests just couldn't declare it.

hermes_cli/mcp_catalog.py

@@ -77,6 +77,10 @@ class TransportSpec:
     args: List[str] = field(default_factory=list)
     url: Optional[str] = None
     version: Optional[str] = None  # informational, pinned
+    # Static environment variables for the stdio subprocess (e.g. telemetry
+    # opt-outs, mode flags). NOT for secrets — credentials go through
+    # auth.env so they are prompted for and land in ~/.hermes/.env.
+    env: Dict[str, str] = field(default_factory=dict)
 
 
 @dataclass
@@ -184,12 +188,20 @@ def _parse_manifest(path: Path) -> CatalogEntry:
     args = transport_raw.get("args") or []
     if not isinstance(args, list):
         raise CatalogError(f"{path}: transport.args must be a list")
+    env_raw = transport_raw.get("env") or {}
+    if not isinstance(env_raw, dict) or not all(
+        isinstance(k, str) and isinstance(v, str) for k, v in env_raw.items()
+    ):
+        raise CatalogError(
+            f"{path}: transport.env must be a mapping of string to string"
+        )
     transport = TransportSpec(
         type=t_type,
         command=transport_raw.get("command"),
         args=[str(a) for a in args],
         url=transport_raw.get("url"),
         version=transport_raw.get("version"),
+        env=dict(env_raw),
     )
     if t_type == "stdio" and not transport.command:
         raise CatalogError(f"{path}: stdio transport requires 'command'")
@@ -468,6 +480,8 @@ def _build_server_config(
         cfg["command"] = _expand_install_dir(t.command or "", install_dir)
         if t.args:
             cfg["args"] = [_expand_install_dir(a, install_dir) for a in t.args]
+        if t.env:
+            cfg["env"] = dict(t.env)
     elif t.type == "http":
         cfg["url"] = t.url
         if entry.auth.type == "oauth":