feat: extend tool_arg_contract with type checking (Closes #1529)

[Lexus2016]

Summary

Extends check_tool_args_contract() to validate basic JSON Schema types (string, integer, number, boolean, array, object, null) in addition to the existing required + enum checks.

Changes

• agent/tool_arg_contract.py: Added _SCHEMA_PY_TYPES mapping, _check_type() helper, and ArgContractViolation.type_mismatch classmethod. Type validation runs alongside enum checks in the existing property loop. Fail-open when no type declared. null type matches only None. integer explicitly excludes bool.
• tests/agent/test_tool_arg_contract.py: 13 new test cases covering type matches, mismatches, union types, fail-open cases, and combined type+enum violations.

Context

• Parent issue: [FIX] Systemic parse-error across 8 tools — 484 events/7d, common root cause in argument generation, not per-tool bugs #1487 (systemic parse-error — 484 events/7d across 8 tools)
• Audit ([FIX] Audit native tool schemas for contract-check compatibility (#1487 child A) #1528) confirmed all 8 tools already have required declarations; the missing layer was type validation
• Logic mirrors tools/tool_search.py:validate_tool_args() / _check_type() for discovered tools, now available at the native-tool composition boundary
• Default-OFF gating unchanged — still opt-in via HERMES_TOOL_ARG_CONTRACT env or tool_arg_contract.enabled config

Checklist

• Lint passes (ruff check)
• Format passes (ruff format --check)
• 45 tests pass (was 32, added 13)
• Lines changed: 214 (additive, minimal surface)

Closes #1529

[Lexus2016]

Closing as duplicate: PR #1531 implements the same type-checking feature (Closes #1529) and additionally closes #1528 (schema audit). #1531 was merged to main. This v2 branch is superseded.