[codex] feat: add breadcrumb navigation trail

[shinzoxD]

Summary

• Add a reusable token-styled Breadcrumb component with nav + ordered-list semantics.
• Mark only the final segment with aria-current=page and keep it non-linking.
• Truncate long current-page labels through the shared truncateMiddle helper.
• Wire breadcrumbs into VaultDetail, VaultTransactions, and ValidationDetail.
• Add component tests and design-system documentation.

Closes #454

Validation

• Passed: .\node_modules\.bin\vitest.cmd run src/components/__tests__/Breadcrumb.test.tsx --environment jsdom --coverage=false
• Failed, existing baseline: .\node_modules\.bin\tsc.cmd -b --pretty false stops on unrelated syntax/conflict-marker errors in ConfirmationModal.tsx, PendingValidations.tsx, PendingValidations.test.tsx, and csv.analytics.test.ts.
• Timed out, existing baseline: npm test ran for 120s and hit existing failures such as undefined createMilestoneRow in CreateVault and undefined ShortcutsHelp in Layout.
• Failed, existing baseline: VaultDetail.test.tsx still fails on undefined isValid in AddressDisplay and undefined mockDownloadIcsEvent in the test file.

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[shinzoxD]

Small improvement pushed in commit d57b9a7:

fix(breadcrumb): add title tooltip to truncated ancestor segments

Previously, only the current (last) breadcrumb segment had a title tooltip when truncated. Ancestor segments clipped by CSS text-overflow: ellipsis (maxWidth 12rem) showed no full text on hover. This adds title={segment.label} to both the ancestor <span> and <Link> elements.

Verification:

• Breadcrumb.test.tsx: 5 passed ✅
• Pre-existing TypeScript errors in unrelated files (ConfirmationModal.tsx, PendingValidations.tsx, etc.) are not caused by this change
• Pre-existing test failures in unrelated suites (dashboard utils, WalletContext, Analytics) are not affected