Summary

Allow consolidated issue_write and granular update_issue_type to remove an issue type with an explicit empty-string input.

Why

Related: github/plan-track-agentic-org#193

GitHub's REST API removes an issue type with "type": null, while both MCP tools already expose their issue-type input as a string. We use an empty string at the MCP boundary because it:

• preserves the existing string-only schemas and generated client/docs behavior;
• distinguishes omission (leave the current type unchanged) from an explicit clear; and
• keeps this fix in the server tools without requiring MCP App or docs-generator changes.

The server translates the empty string into one REST PATCH containing "type": null.

What changed

• Treat an explicitly supplied empty type or issue_type as a clear operation.
• Preserve existing behavior for omitted inputs and non-empty type names.
• Add focused schema and request-body coverage for consolidated and granular tools.

MCP impact

• No tool or API changes
• Tool behavior changed - empty issue type inputs remove the current type.
• New tool added

Prompts tested (tool changes only)

• "Set this issue type to Bug"
• "Remove the type from this issue"

Security / limits

• No security or limits impact - this uses the existing issue update permission and endpoint.
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Focused tests cover omitted, non-empty set, empty-string clear, create omission, required granular input, and exact PATCH JSON. Live validation with the locally built stdio server confirmed both clear paths read back type: null on a disposable issue that was then closed.

Docs

• Not needed
• Generated tool reference artifacts updated; generator unchanged