[Transactions] Batch Operation Summary #511

Goal

Decode a pasted transaction envelope with multiple operations and show an aggregate summary: counts by operation type, total native amount moved, and every distinct source account referenced, without submitting anything.

Data source: Pasted transaction envelope XDR decoded locally with the Stellar SDK; fully offline.

This issue is independent of every other new-season issue. Implement it entirely in features/batch-operation-summary/; the generated registry handles routing, search and navigation. Do not require another feature or pull request to land first.

Acceptance criteria

• Decode every operation in the envelope, including operation-level source account overrides.
• Count operations by type and show the count table alongside the overall operation total.
• Sum native XLM amounts moved by payment and path-payment operations using exact arithmetic, labeled as native-only.
• List every distinct source account referenced, separating the transaction source from operation-level overrides.
• Reject malformed or oversized XDR before rendering any values.

At least 35 meaningful file changes

Start with npm run new:feature -- batch-operation-summary "Batch Operation Summary" transactions. The scaffold supplies the standard 23-file shape; add the twelve task-specific files below and replace all placeholders with working behavior. Every listed file must contain relevant implementation, coverage, fixture data or documentation; empty or duplicated files do not count. A PR may change more than 35 files inside this slice when justified.

Error outcomes

• empty_xdr: map to specific, actionable copy and cover with a test
• invalid_xdr: map to specific, actionable copy and cover with a test
• unsupported_operation: map to specific, actionable copy and cover with a test
• too_large: map to specific, actionable copy and cover with a test

Shared quality bar

• Use Result<T, Code> for expected failures; keep all user-facing copy in copy.ts.
• Cover idle, loading, success and error states. For fully offline tools, loading may be a brief local-processing state.
• Use strings and BigInt for Stellar amounts; never accept, display, store or transmit secret keys.
• Derive valid Stellar addresses from fixed seeds in fixtures; mock requests with MSW.
• Test normal, boundary, malformed-input and transport cases where applicable, plus at least two accessibility states.
• Pass npm run check and npm run verify:features -- batch-operation-summary.
• Keep the pull request inside features/batch-operation-summary/.

This tool is fully offline. Set networks: [] and offline: true in the manifest, and export an empty MSW handler array.

Implementation note: Only native XLM amounts can be summed meaningfully across mixed operation types without a shared unit; issued-asset amounts must stay broken out per asset identity, never merged into the native total.

Reference slice: features/preconditions-explainer; also read the feature contract.

Out of scope

• No transaction signing or submission.
• No per-operation result evaluation.