feat: add extraction schema, sidebar nav, few-shot prompting, and prompt settings

Overhaul extraction pipeline with new TradeItem model, conversation flow,
and dedicated extraction endpoint. Add sidebar navigation with NavMenu
component and landing page. Introduce few-shot prompting service and
tests. Add prompt settings and email upload specs. Update OpenSpec
tooling with improved export-spec and extract-feature commands. Archive
completed changes and export full specs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/commands/opsx/extract-feature.md

@@ -105,6 +105,7 @@ Print it, take it to the sandbox, type it in.
 - Mark domain-specific code clearly so the user knows what to adapt vs copy verbatim
 - Keep each step self-contained — the user may take breaks between steps
 - If a feature spans more than ~200 lines of stripped code, warn the user and suggest using `/opsx:export-spec` instead
+- If the feature has UI components, warn that the code recipe does not capture layout context (AppBar height, sidebar width, container sizing). Suggest `/opsx:export-spec` for UI-heavy features — it includes a Target Layout section with ASCII diagram and integration guidance
 - Output must be valid markdown that renders well when printed
 - When in cumulative mode, skip superseded code — always use the latest version of each file
 - In the output header, show which changes were included and which were skipped