test: manifest graph and diff graph component unit tests (#1956)

* test: add manifest graph and diff graph component unit tests

Extend test coverage for manifest-graph.tsx and manifest-diff-graph.tsx,
adding 53 new tests covering node hover highlighting, edit resource modal,
fullscreen button, additional node types (payment_rail, party_type, mapping,
operational_gateway, provider_connection, instruction_route, market_data),
double-click navigation for all node types, filter sidebar selection
clearing, edge rendering, modified node detection, edge diff visualization,
diff legend, combined diff states, and all 13 diff node type variants.

* fix: remove unused fireEvent import in diff graph tests

* test: address review feedback - add missing node types and edge assertions

- Add market_data, organization, internal_account to fullManifest and
  navManifest test fixtures for full node type coverage
- Add render and double-click navigation tests for all three types
- Add edge count assertions to zero-count diff summary test

* test: add missing KWH instrument to valuation rule fixtures

Addresses review feedback about inconsistent fixture data where
valuation rules referenced KWH but it was not in the instruments array.

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Co-authored-by: Ben Coombs <bjcoombs@users.noreply.github.com>

Author: bjcoombs