Internal Architecture Refactoring: Report Pipeline and Provider Model

This release is an internal code quality improvement. There are no changes to CLI behavior,
rendered Markdown output, or user-facing functionality. If your pipelines work today, they will
continue to work the same way after upgrading.

✨ Features

• Explicit report-generation pipeline — ReportModelBuilder has been decomposed into five
  explicit pipeline stages (ResourceChangeStage, AttributeFilteringStage,
  SummaryEnrichmentStage, DisplayFilteringStage, ReportAssemblyStage). Each stage has a
  well-defined input/output contract and can be unit-tested independently.

• Narrower provider contribution model — The broad IProviderModule contract has been
  replaced by a narrower IProvider interface with six optional capability interfaces
  (IResourceFactory, IValueFormatter, IResourceRenderer, IGroupNamingConvention,
  IAttributeFilter, IDetailsSectionProvider). Registered via ProviderContributionSet,
  providers now declare only the capabilities they implement. Adding a new provider capability
  no longer requires editing all existing providers.

• Instance-based role definition resolution — The static mutable AzureRoleDefinitionMapper
  has been replaced by IRoleDefinitionResolver / AzureRoleDefinitionResolver, scoped per
  application run. Custom role definitions loaded from a plan no longer bleed across multiple
  in-process runs, improving correctness in multi-call scenarios.

• Diagnostics decomposition — Diagnostic collection has been split into an append-only
  IDiagnosticSink, an immutable DiagnosticReport snapshot, and a dedicated
  DiagnosticMarkdownFormatter. Producers now append to the sink; reporting is assembled from
  the snapshot, keeping the two concerns separate.

• AzApi render-planning separation — Policy decisions (what to render) have been extracted
  into AzApiBodyRenderPlanner / AzApiBodyRenderPlans, leaving AzApiBodyRenderer focused
  on layout and emission. Similarly, DefaultResourceRenderPolicy now holds the scenario
  detection heuristics for the default renderer.

🔗 Commits

• e3e3a14 feat: complete feature 110 refactoring work
• 2a7ab3d refactor: complete feature 110 review rework for tasks 7-9