feat: add shared transaction summary builder (Closes #90)

[panditdhamdhere]

Summary

Closes #90

Adds a shared review-before-action TransactionSummary model and builders for payment, anchor, and escrow preview screens, with web UI integration, fixtures, tests, and docs. Also restores apps/web/components/ui.tsx and apps/web/app/assets/page.tsx, which were truncated on main and blocked web typecheck/build.

Issue scope

Acceptance Criterion	Status	Implementation Evidence	Tests	Notes
Transaction summary type is implemented	Complete	packages/types TransactionSummary* + packages/validators TransactionSummarySchema	packages/validators/test/summary.test.ts	—
Payment, anchor, and escrow summary cases are supported	Complete	paymentIntentToSummary, anchorRequestToSummary, anchorRecordToSummary, escrowMilestoneToSummary in packages/stellar-kit/src/summary.ts	packages/stellar-kit/test/summary.test.ts	—
Network, asset, memo, and fee information is represented where available	Complete	Summary fields + fee estimate sources (anchor_config / anchor_record / unavailable / manual)	stellar-kit + validators tests	Protocol fee estimation is intentionally unavailable in MVP
Web preview components use the shared summary builder	Complete	TransactionSummaryPanel on payments, anchors, escrow	apps/web/test/transaction-summary.test.ts	Screenshots pending if required by reviewer
Tests cover major summary states	Complete	Payment / deposit / withdrawal / escrow / parse / fixtures	stellar-kit, validators, web	—
Documentation explains summary limitations	Complete	docs/transaction-summary.md	N/A	Linked from docs page + README

Affected packages / apps

• apps/web
• packages/types
• packages/config
• packages/fixtures
• packages/validators
• packages/stellar-kit
• packages/anchor-utils
• contracts/treasury-escrow
• docs/
• Other (list): examples/, scripts/check-examples.mts

Testing performed

• pnpm --filter @anchorkit/types... build
• pnpm --filter @anchorkit/validators... build
• pnpm --filter @anchorkit/stellar-kit... build
• pnpm --filter @anchorkit/stellar-kit test -- summary.test.ts (13 passed)
• pnpm --filter @anchorkit/validators test -- summary.test.ts examples.test.ts (25 passed)
• pnpm check:examples (19 examples, 0 failing)
• pnpm --filter @anchorkit/web test -- transaction-summary.test.ts (4 passed)
• pnpm --filter @anchorkit/web typecheck
• pnpm --filter @anchorkit/web build

CI status: Pending after PR open.

Screenshots / recordings

Before	After
No shared summary panel on payment/anchor/escrow review surfaces	Shared TransactionSummaryPanel on /payments, /anchors, /escrow

Security impact

• This PR touches secret handling, callback URLs, network selection, or contract admin/authorization logic.
• No security-relevant surface touched.

Defaults remain testnet-first. Summaries use public keys only; no secrets in fixtures.

Documentation impact

• Docs under /docs updated for this change.
• README updated (new package, script, or workflow).
• No user-facing behaviour changed — no docs update needed.

Maintainer Review Checklist (self-check)

PR self-check

• References the original issue with Closes #90 in the PR body.
• Acceptance criteria on the issue are checked off individually in the PR description.
• Local package builds + targeted tests + web typecheck/build passed.
• pnpm check:boundaries (run if reviewer requests; package source imports added within existing deps).
• pnpm contract:test N/A — no contract changes.

Stellar network correctness

• New key parsing matches branded types.
• Amounts remain 7-decimal strings.
• Memo rules enforced if touched.
• Horizon error handling N/A — no new Horizon calls.
• No new mainnet-reaching Horizon/RPC calls.

Anchor and SEP flow correctness

• Deposit/withdrawal metadata uses existing request shapes for summary mapping.
• Callback URL validation N/A.
• Lifecycle transitions N/A.
• Exhaustive never checks used in operation headline switch.

Payment intent and readiness correctness

• Payment summaries built from validated PaymentIntent objects.
• Readiness warnings can be passed through as riskNotes.
• Spendable balance model N/A for this PR.

Soroban contract correctness (if contracts/ changed)

• N/A

Secret leakage (R0–R6)

• R0–R6 respected; fixtures use public demo keys only.
• Diff search for secret-key patterns is clean.

Mainnet safety

• Defaults remain testnet-first.
• No new mainnet submission paths.
• No hardcoded mainnet production URLs.

Tests

• New public functions have positive + negative Vitest cases.
• Fixture/example validation covered.
• Tests do not print or assert on raw secrets.

Documentation

• docs/transaction-summary.md added.
• README docs index + web docs nav updated.
• Security docs N/A.