Fix omitted tool arguments

[SamMorrowDrums]

Summary

• treat omitted, nil, and zero-length tools/call arguments as an empty JSON object
• keep explicit null and malformed JSON invalid while allowing parameterized tools to run their existing required-field validation
• add table-driven wrapper coverage and a get_me handler regression test

Rationale

The MCP 2026-07-28 schema makes CallToolRequestParams.arguments optional, but constrains it to an object when present. The shared wrapper now supplies {} only when the raw argument bytes are absent. It deliberately does not handle a missing params object, leaving the go-sdk protocol boundary to reject that required field.

Validation

• script/lint
• script/test

Fixes #2587

This independently authored change supersedes duplicate attempts #2632, #2680, and #2689. No commits were copied or cherry-picked from those branches; this branch starts at origin/main commit 8395beae410e4fe50c4610e2b354a40d21997f45.

[Copilot]

Pull request overview

Fixes omitted tool arguments by normalizing absent payloads to {} while preserving validation failures.

Changes:

• Normalizes nil and zero-length arguments.
• Rejects explicit null and malformed JSON.
• Adds wrapper and get_me regression coverage.

Show a summary per file

File	Description
pkg/inventory/server_tool.go	Normalizes omitted arguments and centralizes errors.
pkg/inventory/server_tool_test.go	Adds table-driven argument handling tests.
pkg/github/context_tools_test.go	Verifies get_me accepts omitted arguments.

Review details

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• Files reviewed: 3/3 changed files
• Comments generated: 0
• Review effort level: Balanced