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>

openspec/changes/archive/2026-04-06-update-extraction-schema/specs/extraction-tools/spec.md

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+## ADDED Requirements
+
+### Requirement: Counterparty lookup tool
+
+The extraction plugin SHALL expose a `lookup_counterparty` Semantic Kernel function that accepts a counterparty name string and calls the external counterparty API. The tool SHALL return a list of candidate (counterparty, legal_entity) tuples.
+
+#### Scenario: Single match found
+
+- **WHEN** the tool is called with a counterparty name that matches exactly one record
+- **THEN** the tool returns a single candidate with the counterparty name and legal entity ID
+
+#### Scenario: Multiple matches found (disambiguation needed)
+
+- **WHEN** the tool is called with a counterparty name that matches multiple records
+- **THEN** the tool returns all matching candidates so the agent can present them to the user for selection
+
+#### Scenario: No match found
+
+- **WHEN** the tool is called with a counterparty name that matches no records
+- **THEN** the tool returns an empty list and an informative message so the agent can ask the user for clarification
+
+### Requirement: Trade validation tool
+
+The extraction plugin SHALL expose a `validate_trade` Semantic Kernel function that accepts a trade ID and calls the external trade validation API to verify the trade exists.
+
+#### Scenario: Valid trade ID
+
+- **WHEN** the tool is called with a known trade ID
+- **THEN** the tool returns a success result confirming the trade exists
+
+#### Scenario: Invalid trade ID
+
+- **WHEN** the tool is called with an unknown trade ID
+- **THEN** the tool returns an error result so the agent can flag it to the user
+
+### Requirement: Currency validation tool
+
+The extraction plugin SHALL expose a `validate_currency` Semantic Kernel function that accepts a currency code and calls the external currency validation API to verify it is a valid ISO currency code.
+
+#### Scenario: Valid currency code
+
+- **WHEN** the tool is called with "GBP"
+- **THEN** the tool returns a success result
+
+#### Scenario: Invalid currency code
+
+- **WHEN** the tool is called with an unrecognized code
+- **THEN** the tool returns an error with suggestions for valid codes
+
+### Requirement: Schema validation tool
+
+The extraction plugin SHALL expose a `validate_schema` Semantic Kernel function that accepts the full ExtractionResult JSON and validates that all required fields are present and correctly typed for every TradeItem.
+
+#### Scenario: Valid extraction result
+
+- **WHEN** the tool is called with a complete and correctly typed ExtractionResult JSON
+- **THEN** the tool returns a success result with no errors
+
+#### Scenario: Missing required fields
+
+- **WHEN** the tool is called with a TradeItem missing the `trade_id` field
+- **THEN** the tool returns a failure result listing the missing fields and which item they belong to
+
+### Requirement: External API configuration
+
+All external API base URLs SHALL be configurable via `appsettings.json` under an `ExternalApis` section. Each tool's HttpClient SHALL read its base URL from configuration at startup.
+
+#### Scenario: Configuration at startup
+
+- **WHEN** the API starts
+- **THEN** it reads external API base URLs from the `ExternalApis` configuration section and configures typed HttpClients accordingly
+
+### Requirement: External API error handling
+
+Each tool SHALL handle HTTP errors from external APIs gracefully, returning a structured error message that the LLM agent can reason about rather than throwing exceptions.
+
+#### Scenario: External API unavailable
+
+- **WHEN** a tool calls an external API that is unreachable
+- **THEN** the tool returns an error result with a descriptive message (e.g., "Counterparty API unavailable") so the agent can inform the user