Document reasoning stream support
Drop crate version numbers from the wiki and fix stale feature notes
Remove pinned crate versions (1.0.0 / v1.2.x prose, `tinyagents = "1"` Cargo
snippets → version-less `cargo add`) so the docs don't go stale on every
release. Also correct two spec mismatches the feature removal left behind:
Quick-Start still listed `openai` as an opt-in Cargo feature, and Providers
claimed hosted providers were feature-gated — both now reflect the OpenAI
adapter being compiled in by default.
Document OpenAiModel::list_models and fix stale offline-provider notes
Add a 'Discover available models' section to Providers, correct the
'offline/compiled-in' note (OpenAiModel now ships by default), and index the
list-models capability in Capabilities.
Add agent-friendly Capabilities index and document v1.2.x SDK-gap features
New Capabilities.md master index (per-surface capability tables + Recently-added
section + agent quick-start decision list) linked from Home and the sidebar.
Harness, Graph-Runtime, and Registry pages document the new tool-policy
enforcement, unknown-tool recovery, workspace isolation, tool-exposure auditing,
middleware control precedence, budget reservation/reconcile, stable event ids,
map/reduce timeouts/cancellation, orchestrate_list filters, registry
introspection, and storage conformance. Examples gains runnable snippets per
feature.