Retire obsolete bundled community extensions

[bigsmartben]

Summary

• retire and remove the bundled inception, intake, and repository-governance snapshots
• reduce fresh initialization to the core git extension while keeping discovery and preview bundled as explicit opt-in extensions
• remove retired catalog/package-data entries and route provider evidence blockers to a generic source-evidence workflow
• document the audit decisions and migration behavior
• verify integration upgrades preserve files already present under retired extension directories

User impact

Fresh projects receive a smaller default extension set. Existing project files are not deleted during integration upgrades. Users can still install maintained optional extensions with specify extension add discovery or specify extension add preview.

Validation

• scripts/community/validate-integration.ps1 — passed
• focused extension/init/preset/workflow tests — 851 passed, 11 skipped
• full repository suite — 3711 passed, 257 skipped; 6 Windows-only setup failures because the current account lacks symlink creation privilege (WinError 1314)
• wheel build and content audit — passed; retired snapshots absent, opt-in snapshots present
• git diff --check — passed
• Ruff reports one pre-existing unused import in tests/extensions/test_update_agent_context_feature_json.py; changed files are clean

Closes #85

AI disclosure

Implemented and posted on behalf of @bigsmartben by OpenAI Codex (model: GPT-5, autonomous).

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Align the discovery instructions with the bundled command

For users following this new migration table, discovery is presented as the retained general-purpose technical-research option, but extensions/discovery/extension.yml provides only speckit.discovery.contract; the README's discovery section still directs users to six unavailable commands such as speckit.discovery.feasibility and speckit.discovery.poc. Consequently, after the documented specify extension add discovery, none of the listed invocations work. Update the retained-capability description and command examples to match the focused contract workflow.

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