Add sub-issues, issue types, projects, and issue fields guidance to github-issues skill (#884)

* Add issue fields, issue types, and list_issue_types to github-issues skill

- Add list_issue_types to available MCP tools table
- Add type parameter to optional parameters with guidance
- Expand issue types section: MCP tools (preferred) + GraphQL (advanced)
- Document org-level type discovery, create/update with type, GraphQL mutations
- Add issue fields section: discover, read, set via GraphQL
- Note required GraphQL-Features headers (issue_fields, issue_types)
- Update skill description to mention fields, types, dates, priority

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add Projects V2 guidance to github-issues skill

Include MCP tools (projects_list, projects_get, projects_write) and
GraphQL examples for project item management.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add sub-issues section, move issue fields to end with preview note

- Add Sub-Issues and Parent Issues section (MCP, REST, GraphQL)
- Add issue_read tool to MCP tools table
- Move Issue Fields to last section with private preview callout
- Link to community discussion for requesting access

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Prefer issue types over labels for categorization

Update guidance and examples to use type parameter (Bug, Feature)
instead of equivalent labels when issue types are available.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Prefer issue fields over project fields for metadata

Issue fields live on the issue and travel across projects.
Project fields are scoped to a single project.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add issue dependencies (blocked by/blocking) section

Covers REST endpoints (list, add, remove) and GraphQL
(blockedBy, blocking, issueDependenciesSummary, mutations).
Also documents tracked issues read-only fields.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add project discovery workflow for progress reports

Teach agents how to find projects by name, discover fields
and iterations, paginate items, and build status breakdowns.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Generate updated skill listing after SKILL.md changes

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Split skill into reference files per reviewer feedback

Move sub-issues, dependencies, issue types, projects, and issue fields
into separate references/ files. Main SKILL.md now contains core MCP
workflow and a capability table pointing to each reference. This way
the agent only loads the knowledge it needs for the specific task.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

docs/README.skills.md

@@ -120,7 +120,7 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-skills) for guidelines on how to
 | [git-commit](../skills/git-commit/SKILL.md) | Execute git commit with conventional commit message analysis, intelligent staging, and message generation. Use when user asks to commit changes, create a git commit, or mentions "/commit". Supports: (1) Auto-detecting type and scope from changes, (2) Generating conventional commit messages from diff, (3) Interactive commit with optional type/scope/description overrides, (4) Intelligent file staging for logical grouping | None |
 | [git-flow-branch-creator](../skills/git-flow-branch-creator/SKILL.md) | Intelligent Git Flow branch creator that analyzes git status/diff and creates appropriate branches following the nvie Git Flow branching model. | None |
 | [github-copilot-starter](../skills/github-copilot-starter/SKILL.md) | Set up complete GitHub Copilot configuration for a new project based on technology stack | None |
-| [github-issues](../skills/github-issues/SKILL.md) | Create, update, and manage GitHub issues using MCP tools. Use this skill when users want to create bug reports, feature requests, or task issues, update existing issues, add labels/assignees/milestones, or manage issue workflows. Triggers on requests like "create an issue", "file a bug", "request a feature", "update issue X", or any GitHub issue management task. | `references/templates.md` |
+| [github-issues](../skills/github-issues/SKILL.md) | Create, update, and manage GitHub issues using MCP tools. Use this skill when users want to create bug reports, feature requests, or task issues, update existing issues, add labels/assignees/milestones, set issue fields (dates, priority, custom fields), set issue types, or manage issue workflows. Triggers on requests like "create an issue", "file a bug", "request a feature", "update issue X", "set the priority", "set the start date", or any GitHub issue management task. | `references/dependencies.md`<br />`references/issue-fields.md`<br />`references/issue-types.md`<br />`references/projects.md`<br />`references/sub-issues.md`<br />`references/templates.md` |
 | [go-mcp-server-generator](../skills/go-mcp-server-generator/SKILL.md) | Generate a complete Go MCP server project with proper structure, dependencies, and implementation using the official github.com/modelcontextprotocol/go-sdk. | None |
 | [image-manipulation-image-magick](../skills/image-manipulation-image-magick/SKILL.md) | Process and manipulate images using ImageMagick. Supports resizing, format conversion, batch processing, and retrieving image metadata. Use when working with images, creating thumbnails, resizing wallpapers, or performing batch image operations. | None |
 | [import-infrastructure-as-code](../skills/import-infrastructure-as-code/SKILL.md) | Import existing Azure resources into Terraform using Azure CLI discovery and Azure Verified Modules (AVM). Use when asked to reverse-engineer live Azure infrastructure, generate Infrastructure as Code from existing subscriptions/resource groups/resource IDs, map dependencies, derive exact import addresses from downloaded module source, prevent configuration drift, and produce AVM-based Terraform files ready for validation and planning across any Azure resource type. | None |