feat: add organization issue fields config export wiring

[joshjohanning]

Why

The companion sync action now supports organization issue fields, so this repo needs to export and provide issue field config per org for end-to-end testing before release.

What changed

• Added config/issue-fields.yml in the action-compatible schema.
• Included the current org issue fields (Priority, Start date, Target date, Effort) with their data types, visibility, and single-select option values.
• Wired issue-fields-file into the org entry in orgs.yml.
• Added the matching delete-unmanaged-issue-fields drift-control comment beside related toggles.

Notes

• The issue field values were taken from the authenticated org settings view because the local CLI token lacked admin:org scope for direct API reads at execution time.
• Single-select colors use API enum names (pink, red, yellow, green) and priorities are preserved in display order.

[Copilot]

Pull request overview

Adds organization-level issue fields configuration export to this repo and wires it into orgs.yml so the bulk org settings sync workflow can apply (and optionally drift-control) issue field definitions during end-to-end testing.

Changes:

• Added config/issue-fields.yml defining org issue fields (Priority, Start date, Target date, Effort) with types, visibility, and select options.
• Wired the new config into orgs.yml via issue-fields-file.
• Added the corresponding drift-control toggle comment delete-unmanaged-issue-fields alongside existing unmanaged-delete options.

Show a summary per file

File	Description
orgs.yml	Adds issue-fields-file wiring and a matching drift-control toggle comment for unmanaged issue fields.
config/issue-fields.yml	Introduces the action-compatible org issue fields definitions (single-select and date fields) for syncing.

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