llm-migrate v1.5.2

Precision and honesty patch, driven by a real v1.5.1 guided run of a
production Bedrock application whose config-driven prompt library produced
zero prompt tasks and whose report raised problems without directions. No
schema version changed; every contract change is an additive field.

• Prompt consumers are recorded only on model invocations or provider-client
  calls; helpers taking input= no longer inflate the consumer count.
• Out-of-scope prompt files: prompts referenced only by another model's
  configuration profile, and unreferenced candidates beside selected
  siblings, move from unknowns to the plan's new out_of_scope list and are
  never prepared.
• Unknowns the scan already answers (for example parallel_tool_use in an
  app with no tools) are not raised; the XML-formatting finding is dropped on
  same-provider moves.
• Known evidence includes every source URL recorded in the run's resolved
  registry profiles and pair knowledge; change review shows each citation's
  verification state (registry-recorded, plan-carried, or UNKNOWN).
• Evidence-backed validation: generated_tests needs the user's passing
  outcome and summary line, and byok_evaluation needs the evaluation-run
  artifact bound to the finalized manifest. Finalize re-checks the binding
  and reports NOT VALIDATED otherwise (a strict violation).
• Whole-application source-reference sweep: finalize reports any scanned
  file still naming the source model that nothing accounts for
  (source_reference_uncovered; strict blocks). Intentional mentions close
  through confirm_unaffected(acknowledge_source_references=true) with the
  user's rationale.
• Registry guidance about structured output, tool use, or reasoning is
  pre-disposed not applicable, with the reason, when the application never
  exhibits the trigger under fully resolved prompt coverage.
• The run report opens with "Action required" and gives unknowns an Action
  column; run status warns while prompt coverage is incomplete and states
  the two-pass validation flow; server instructions order review before
  finalize; MCP start_migration returns paths relative to the run root.
• README documents per-host MCP registration and verification.