Add Spec Kit TLDR extension to community catalog

[mnriem]

Adds the Spec Kit TLDR extension (tldr) submitted by @qurore to the community catalog.

Closes #2987

Validation summary

• ✅ Repository exists and is public: https://github.com/qurore/speckit-tldr
• ✅ extension.yml, README.md, and LICENSE present in repo
• ✅ GitHub release v0.3.0 exists
• ✅ Download URL accessible (HTTP 200) and follows archive/refs/tags/vX.Y.Z.zip pattern
• ✅ Extension ID tldr is lowercase-with-hyphens
• ✅ Version 0.3.0 follows semver
• ✅ Submission checklists all checked
• ✅ Catalog JSON validated

Changes

• extensions/catalog.community.json — new tldr entry in alphabetical order (git listed as optional tool dependency)
• docs/community/extensions.md — new row in the community extensions table

cc @qurore

[Copilot]

Pull request overview

This PR adds the Spec Kit TLDR community extension (tldr) to Spec Kit’s community extension catalog and documentation, making it discoverable and installable via the standard community catalog flow.

Changes:

• Added a new tldr entry to extensions/catalog.community.json, including optional git tool dependency metadata.
• Added a new “Spec Kit TLDR” row to the community extensions table in docs/community/extensions.md.

Show a summary per file

File	Description
extensions/catalog.community.json	Adds the tldr community extension entry (id-sorted, includes requires/tools + metadata fields).
docs/community/extensions.md	Adds the “Spec Kit TLDR” row to the community extensions table (name-sorted).

Copilot's findings

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