fix(mcp): return typed error JSON for unsupported actions (info/describe/list-filter) (#2989)
`claw mcp info nonexistent --output-format json` and
`claw mcp list nonexistent --output-format json` fell through to
the generic help renderer, returning an opaque envelope with only
`unexpected` set — no machine-readable error_kind.
Fix:
- Add typed guards in render_mcp_report_for/_json_for for:
- `list <filter>`: list accepts no filter argument
- `info <name>` / `describe <name>`: suggest `mcp show`
- New render_mcp_unsupported_action_text/json helpers emit
`ok:false`, `error_kind:"unsupported_action"`, `hint`, `requested_action`
- `mcp show`, `mcp list`, `mcp help` existing paths unchanged
Test: mcp_unsupported_actions_return_typed_error_not_generic_help
asserts kind=="mcp", ok==false, error_kind=="unsupported_action"
for info/list-filter/describe paths.
Pinpoint: ROADMAP #504
5eb4b8a944