Add community bundle submission path

[SiCar10mw]

Summary

• Add a Bundle Submission issue form for community bundle metadata, validation evidence, component catalog requirements, and proposed bundle catalog entry data.
• Add a Community Bundles docs page and wire it into the community overview, docs table of contents, and README community section.
• Document bundle publishing expectations in the bundles reference, especially that bundle component references must resolve through bundled, installed, or active component catalogs.

This intentionally does not add a bundle catalog entry or change bundle runtime resolution. The dependency-resolution and install policy decision is tracked in #3161.

Validation

• uv run python YAML parse check for .github/ISSUE_TEMPLATE/bundle_submission.yml and docs/toc.yml
• git diff --check
• uv run pytest tests/contract/test_catalog_schema.py tests/contract/test_bundle_cli.py -q
• Reviewed the updated diff with local Claude CLI and Gemini CLI; second pass reported no blocking issues

DocFX build was not run locally because dotnet/docfx are not installed in this environment.

Refs #3161

[Copilot]

Pull request overview

Adds a community-facing submission path for Spec Kit bundles, aligning bundles with existing community contribution lanes (extensions/presets) via a dedicated issue form and documentation updates. This complements the existing bundle CLI/docs by clarifying publishing expectations and the component-catalog resolution requirement called out in #3161, without changing runtime behavior.

Changes:

• Adds a new GitHub Issue Form for community bundle submissions (bundle_submission.yml).
• Introduces a Community Bundles docs page and links it from the community overview and docs TOC.
• Expands bundle publishing guidance in the bundles reference and README to emphasize component resolution via bundled/installed/active catalogs.

Show a summary per file

File	Description
README.md	Adds Bundles to the community links and points contributors to the new Community Bundles guide + submission template.
docs/toc.yml	Wires the new Community Bundles page into the documentation navigation.
docs/reference/bundles.md	Documents “Publish a Bundle” expectations, including dependency/component catalog resolution constraints.
docs/community/overview.md	Adds a Bundles section to the community landing page.
docs/community/bundles.md	New Community Bundles page covering submission requirements, resolution expectations, and review scope.
.github/ISSUE_TEMPLATE/bundle_submission.yml	New issue form capturing bundle metadata, validation evidence, required catalogs, and proposed catalog entry.

Copilot's findings

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• Files reviewed: 6/6 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 6/6 changed files
• Comments generated: 1

[mnriem]

Please address Copilot feedback

[Copilot]

Copilot's findings

• Files reviewed: 6/6 changed files
• Comments generated: 3

[mnriem]

Please address Copilot feedback

[Copilot]

Review details

• Files reviewed: 6/6 changed files
• Comments generated: 1
• Review effort level: Low

[mnriem]

Please address Copilot feedback