Extension/SDK/RPC registerTool defaulted an omitted loadMode to
"discoverable". A UI-only re-register of an essential built-in
(read/write/bash/edit/glob) then became discoverable and, with tools.xdev
on, was unmounted from the top-level schema. read/write dropping also
broke the xd:// transport (read xd://, write xd://<tool>), leaving the
model with no callable coding essentials.
- Add defaultLoadModeForToolName: omitted loadMode resolves to "essential"
for known essential built-in names, "discoverable" otherwise.
- Apply it at all four adapter boundaries (extension wrapper, custom-tools
wrapper, sdk customToolToDefinition, rpc normalizeHostToolDefinitions).
- Transport invariant: read/write never mount under xdev regardless of
loadMode (they carry the transport).
- Regression test covering the demotion, transport invariant, and a drift
guard tying the essential-name set to the tool classes.
Fixes#5764
usr-bin-roygbiv