…in Workflow Insight

The previous default Bedrock model for the Workflow Insight extension's AI
features (us.anthropic.claude-sonnet-4-20250514-v1:0) is deprecated. Updates the
default to the Claude Sonnet 5 US inference profile, makes the model field much
easier to get right, and adapts the Converse calls to Sonnet 5's inference
parameters.

- Default model id is now "us.anthropic.claude-sonnet-5" (the US cross-region
  inference profile, matching the prior default's shape) in config.ts,
  DEFAULT_SETTINGS, the package.json setting default, the field placeholder,
  and the README example.
- The Bedrock Model ID field is now an Autosuggest: it offers the models your
  account can use as suggestions AND still accepts any value typed directly
  (useful for profiles/regions the list doesn't surface).
- New "List available models" button fetches models for the currently
  configured Region and AWS Profile via a new host module (bedrockModels.ts):
    - Combines system-defined inference profiles (ListInferenceProfiles,
      paginated) with on-demand, ACTIVE, text-output foundation models
      (ListFoundationModels), de-duplicated and sorted.
    - Base ids that only support the INFERENCE_PROFILE type are skipped (not
      directly invokable — the matching profile already covers them).
    - Reflects models AVAILABLE in the Region; a listed id may still require
      model access to be granted in the Bedrock console (noted in the UI).
- Adds the @aws-sdk/client-bedrock dependency for the control-plane list calls.
- Wiring: a "listModels" message resolves the region/profile from the unsaved
  form (configFromWireSettings) and posts a "bedrockModels" result back;
  failures render inline in the Settings modal rather than as a global toast.
- Temperature handling: Claude Sonnet 5 (adaptive reasoning always on) rejects
  the `temperature` inference parameter ("`temperature` is deprecated for this
  model"). A new bedrockConverse.ts wraps every Converse call: it drops
  temperature up front for models known to reject it (Claude 5-gen and newer)
  and, as a safety net, retries once without temperature on any error that
  mentions it. All three llm.ts call sites and the agentLoop.ts call route
  through this helper. The helper lives in its own vscode-free module so the
  agent loop doesn't pull the VS Code API into its import graph.

Tests: bedrockModels.test.ts (merge/dedupe/sort, filtering, pagination) and
bedrockConverse.test.ts (model detection, up-front strip, error-retry, and
non-temperature errors rethrown). Host suite 168 passing; host + webview
typecheck and builds green.