[StevenTCramer]

Summary

What changed

• source/timewarp-nuru-analyzers/generators/emitters/json-args-emitter.assign.cs: the ValueShape.Json
  assign wraps JsonSerializer.Deserialize in try/catch (Exception) when (NuruBindError.IsJsonMemberFailure(...)), sets __ok = false and records
  NuruBindError.ForJsonMember(key, pattern, exception). The route pattern is threaded in from EmitFill
  (json-args-emitter.validation.cs). The bind method then returns the failure like any scalar bind error,
  so --json-args, TryBind, the daemon and McpHost all report it as a bind error.
• source/timewarp-nuru/invocation/nuru-bind-error.cs: two public static helpers called by generated code.
  IsJsonMemberFailure is true for JsonException, NotSupportedException, InvalidOperationException
  and FormatException (a typed-ID converter that parses text). ForJsonMember builds an InvalidValue
  error: Error: Invalid value for '<key>' on '<pattern>'. <key>: <json path>: <serializer message without the " Path: … | LineNumber …" suffix>. No stack trace.
• documentation/user/features/agent-invocation.md: one bullet on JSON-member failures being
  InvalidValue.
• Tests: tests/timewarp-nuru-mcphost-tests/mcphost-06-json-member-bind-errors.cs (also in the CI
  multi-mode assembly). An [Operation] with IReadOnlyList<JbStep> Steps and JbOptions? Options covers
  an unknown enum name in an array item (Steps: $[0].Tool), a nested-object type mismatch
  (Options: $.Limits.Max) and an unparsable nested Guid (Steps: $[0].Target). It checks TryBind
  (kind InvalidValue, key, message, no stack trace), in-process --json-args with plain errors (exit 1),
  with UseProblemRendererForErrors() and with --no-daemon (exit 1, error=Invalid), McpHost in process
  (isError, error=Invalid), and forwarded through a real NuruDaemonServer for McpHost and for the CLI
  via AddServeRoute() (same text as in process). A handler exception stays error=Faulted over McpHost
  (local and forwarded) and still escapes the in-process CLI as itself.

Gates

Gate	Command	Result
Build	./bin/dev build	Pass, 0 warnings, 0 errors
Test	./bin/dev test	Pass: CI multi-mode 2190 total, 2184 passed, 6 skipped, 0 failed; standalone phase 0 failed
Audit	ganda repo audit	Pass: 44 passed, 0 failed, 1 skipped (after --fix for the advisory vscode-window-icon; see ## Session)

Test plan

Smoke:

ganda runfile cache --clear
dotnet run tests/timewarp-nuru-mcphost-tests/mcphost-06-json-member-bind-errors.cs

Expect: 5 tests pass. Before this change the in-process --json-args cases crash with an unhandled
System.Text.Json.JsonException, and McpHost reports error=Faulted instead of error=Invalid.

Kanban task 530
Session: Roslynk