feat: build policy simulation sandbox modal for testing transaction rules

[feyibosslady]

Closes #58

Description

Before enforcing spending policies on live AI agents, administrators need a simulation sandbox to test hypothetical transactions against existing Zod-validated rule sets and see whether they pass or trigger approval workflows.

This PR adds a Policy Sandbox Modal where users can input test transaction parameters (recipient address, amount, asset type), select which spending policy rules to evaluate, and run simulations to see clear pass/fail results with detailed violation messages.

Changes

New files:

• src/features/policies/utils/simulator.ts — Pure evaluation utility that tests a transaction against PolicyRule objects. Supports all rule fields (Transaction Amount, Asset Identifier, Destination Target, Approved Account Whitelist) and operators (equals, greater_than, less_than, contains, in_whitelist).
• src/features/policies/components/PolicySandboxModal.tsx — Accessible modal component with:
  • React Hook Form + Zod validated inputs for recipient address, amount, and asset type
  • Multi-select rule picker with select/deselect all
  • Per-rule pass/fail evaluation cards with detailed violation messages
  • Summary badge indicating compliance or violations found
  • Uses existing Dialog component for accessibility (focus trap, Escape key, overlay dismissal)

Modified files:

• src/features/policies/index.ts — Exports PolicySandboxModal and simulateTransaction

Acceptance Criteria

• Build src/features/policies/components/PolicySandboxModal.tsx
• Implement form inputs for testing parameters using React Hook Form and Zod validation
• Display simulated evaluation results with detailed failure reasons if rules are breached
• Ensure modal trap focus and keyboard escape key handling for accessibility (via Dialog component)
• Pass all checks in npm run typecheck && npm run lint (new files pass cleanly; pre-existing errors in transactions/page.tsx are unrelated)

Testing & Validation

1. Open the modal in the policy management view
2. Submit test transactions that comply with rules (e.g., 5000 XLM) — verify all-pass output
3. Submit test transactions that violate rules (e.g., 60000 USDC — exceeds block threshold) — verify violation details
4. Toggle individual rules on/off and re-run to confirm selective evaluation
5. Verify npm run typecheck and npm run lint pass for the new files

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[mergekeeper]

Needs review

Linked to #58, but the diff does not match the issue scope.

The pull request includes unrequested wallet feature files which are out of scope for issue #58.

Reviewed commit: fee0b1a4e47e65a097124feb4b133428a7e27177.