Fix GraphQL call using the wrong case for method derivation

[moritzheiber]

Summary

Fixes create_iteration_field, which failed at runtime because the GraphQL mutation selected projectV2field (lowercase) instead of the schema's projectV2Field.

Why

The inner ProjectV2Field struct fields in createIterationField had no graphql: tag, so shurcooL/githubv4 auto-derived the selection name and mis-cased the word boundary after the embedded V2, producing projectV2field. GitHub's API rejected this, blocking iteration field creation entirely.

Fixes #

What changed

• Added explicit `graphql:"projectV2Field"` tags to the createProjectV2Field and updateProjectV2Field mutation structs in projects.go.
• Made the test matchers in projects_v2_test.go schema-faithful (tagged projectV2Field) so they reproduce the bug and guard against the casing regression.

MCP impact

• No tool or API changes — tool schema is unchanged; this is a runtime GraphQL fix only.

Prompts tested (tool changes only)

• N/A (no tool schema changes)

Security / limits

• No security or limits impact

Tool renaming

• I am not renaming tools as part of this PR

Lint & tests

• Linted locally with lint
• Tested locally with test

Docs

• Not needed

[Copilot]

Pull request overview

Fixes a runtime GraphQL mutation failure in create_iteration_field caused by shurcooL/githubv4 auto-deriving the wrong selection name casing (projectV2field vs projectV2Field) when no explicit graphql: tag is present on the nested ProjectV2Field selection.

Changes:

• Added explicit graphql:"projectV2Field" tags to the nested ProjectV2Field selections in the createProjectV2Field and updateProjectV2Field mutations.
• Updated GraphQL mock matchers in projects_v2_test.go to require the schema-faithful projectV2Field selection, preventing regressions.

Show a summary per file

File	Description
pkg/github/projects.go	Adds explicit GraphQL selection tags to ensure correct field casing in mutations used by create_iteration_field.
pkg/github/projects_v2_test.go	Updates mutation matchers to assert the correct projectV2Field selection name and guard against casing regressions.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 0