PolicyRegistry: drop ChildPoliciesOutsideOfRange args, add composite child-count getters

[rayyan224]

Summary

• Removes the (min, max) args from IPolicyRegistry.ChildPoliciesOutsideOfRange; it now reverts with no args.
• Adds two new view functions to IPolicyRegistry: MIN_COMPOSITE_CHILD_POLICIES() and MAX_COMPOSITE_CHILD_POLICIES(), so the valid composite child-count range is discoverable via a call instead of parsed from the error args.
• MockPolicyRegistry implements the new getters as public constants aliasing the existing MIN_CHILD_POLICIES/MAX_CHILD_POLICIES internal constants (same pattern already used for ALWAYS_ALLOW_ID/ALWAYS_BLOCK_ID), and both revert sites (createCompositePolicy, updateComposite) now throw the argless error.
• Updates existing PolicyRegistry unit tests' revert expectations/NatSpec to match, and adds compositeChildPolicyLimits.t.sol covering the two new getters.

Test plan

• forge build — compiles clean, MockPolicyRegistry still satisfies IPolicyRegistry
• forge test --match-path "test/unit/PolicyRegistry/*" — 135 passed, 0 failed
• forge test (full suite) — 715 passed, 0 failed

[github-actions]

Interface Coverage

✅ All interface functions have test coverage.

[github-actions]

📊 Forge Coverage (src/lib/)

🟡 ≥95% across all metrics — some metrics below 99%.

File	Lines	Stmts	Branches	Funcs
🔴 B20FactoryLib.sol	95.40%	96.00%	100.00%	90.00%
🔴 test/lib/ForceFeeder.sol	0.00%	0.00%	100.00%	0.00%
🔴 test/lib/PrecompileProbe.sol	0.00%	0.00%	0.00%	0.00%
🟢 MockActivationRegistry.sol	100.00%	100.00%	100.00%	100.00%
🟢 MockActivationRegistryStorage.sol	100.00%	100.00%	100.00%	100.00%
🟢 MockB20.sol	100.00%	100.00%	100.00%	100.00%
🟢 MockB20Asset.sol	100.00%	100.00%	100.00%	100.00%
🟡 MockB20Factory.sol	98.96%	99.10%	100.00%	100.00%
🟢 MockB20Stablecoin.sol	100.00%	100.00%	100.00%	100.00%
🟢 MockB20Storage.sol	100.00%	100.00%	100.00%	100.00%
🟡 MockPolicyRegistry.sol	100.00%	99.54%	97.67%	100.00%
🟢 MockPolicyRegistryStorage.sol	100.00%	100.00%	100.00%	100.00%
Total	96.80%	97.29%	98.14%	96.49%

Full report: download artifact. To browse locally: make coverage (runs forge coverage + genhtml + opens the HTML report).

[github-actions]

⚠️ Fork tests: 12 failed, 705 passed

These failures indicate divergences where base/base needs to catch up to the base-std spec. This check is advisory and does not block merging.

Failing tests

• test_createCompositePolicy_revertOrder(uint8): Error != expected error: custom error 0xcbdee0f6: != ChildPoliciesOutsideOfRange(); counterexample: calldata=0x5fafe4f70000000000000000000000000000000000000000000000000000000000000004 args=[4]
• test_createCompositePolicy_revert_childPoliciesOutsideOfRange(address,address,uint8,uint8): Error != expected error: custom error 0xcbdee0f6: != ChildPoliciesOutsideOfRange(); counterexample: calldata=0xb84664360000000000000000000000005d9206854c5e4d15896063c7ad4338d3166882fe000000000000000000000000d2926c99164e654182f9f276782e464779c2671000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005 args=[0x5d9206854C5E4d15896063C7ad4338D3166882fe, 0xd2926C99164e654182f9F276782E464779c26710, 0, 5]
• test_updateComposite_revertOrder(uint8): Error != expected error: custom error 0xcbdee0f6: != ChildPoliciesOutsideOfRange(); counterexample: calldata=0x46b240f9000000000000000000000000000000000000000000000000000000000000000d args=[13]
• test_updateComposite_revert_childPoliciesOutsideOfRange(uint8,uint8): Error != expected error: custom error 0xcbdee0f6: != ChildPoliciesOutsideOfRange(); counterexample: calldata=0x25c4476000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001 args=[1, 1]
  [FAIL: custom error 0x54309870] test_maxCompositeChildPolicies_success() (gas: 2586)
  [FAIL: custom error 0xb3ae29f7] test_minCompositeChildPolicies_success() (gas: 2519)

[rayyan224]

Tracked in BOP-497: https://linear.app/coinbase/issue/BOP-497/update-naming-for-error-argument-interface-design-review