Remove dead REST issue-field-value output path

[owenniblock]

Summary

Removes the MinimalIssueFieldValue / MinimalIssueFieldValueSingleSelectOption types and their populator in convertToMinimalIssue. They produce a single_select_option output that is never emitted — GetIssue unconditionally cleared minimalIssue.IssueFieldValues before marshalling, and it was the only caller of convertToMinimalIssue.

Why this is safe (dead-code trace)

• convertToMinimalIssue is the only function that populated MinimalIssue.IssueFieldValues, and its only caller is GetIssue.
• GetIssue set minimalIssue.IssueFieldValues = nil above the feature-flag check — so no flag, code path, or config could surface it.
• single_select_option appeared in zero test/snapshot expectations; two tests explicitly asserted the field was always empty.

History

The REST extraction was added in #2551, then superseded one day later by #2558, which switched get_issue to the GraphQL field_values enrichment path — commit message: "The verbose REST IssueFieldValues is always cleared from the response" — to stay consistent with list_issues/search_issues. The struct + populator were left behind as orphaned code.

Bonus: removes a latent footgun

The struct only modelled single_select_option (go-github's REST IssueFieldValue has no multi-select equivalent), so any future code that resurfaced it would have silently dropped multi-select option data.

What changed

• Remove MinimalIssueFieldValue + MinimalIssueFieldValueSingleSelectOption
• Remove MinimalIssue.IssueFieldValues field (json: issue_field_values)
• Remove the populator loop in convertToMinimalIssue
• Drop the now-redundant nil assignment in GetIssue
• Drop the two test assertions on the removed field (behaviour is now structurally guaranteed; the GraphQL field_values assertions remain)

MCP impact

• No tool or API changes — issue_field_values was omitempty and always empty, so output shape is unchanged. The GraphQL field_values path is unaffected. SearchIssueResult.MarshalJSON still suppresses go-github's own embedded issue_field_values.

Lint & tests

• go build ./..., go vet ./..., go test ./... all pass
• golangci-lint run — 0 issues

[Copilot]

Pull request overview

This PR removes a dead REST-backed issue_field_values output path from the minimal issue types used by issue_read’s get method. The removed structs and population logic were never observable in tool output because the only caller (GetIssue) always suppressed the field prior to marshalling, and the GraphQL field_values enrichment path remains unchanged.

Changes:

• Removed MinimalIssueFieldValue* types and the MinimalIssue.IssueFieldValues field.
• Deleted the REST IssueFieldValues population loop in convertToMinimalIssue and the now-redundant clearing in GetIssue.
• Updated tests to stop asserting on the removed (previously always-empty/omitted) field while preserving GraphQL field_values assertions.

Show a summary per file

File	Description
pkg/github/minimal_types.go	Deletes unused REST-backed minimal issue-field-value types, removes the issue_field_values field from MinimalIssue, and drops the unused population loop.
pkg/github/issues.go	Removes redundant clearing of REST issue field values and keeps GraphQL field_values enrichment behind the feature flag.
pkg/github/issues_test.go	Removes assertions tied to the deleted field and keeps coverage for the GraphQL enrichment behavior.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 0