[codex] update preview extension to v1.1.0

[bigsmartben]

Summary

• Update the bundled preview extension to v1.1.0 from bigsmartben/spec-kit-preview.
• Replace the old single /speckit.preview.html command with six fidelity-specific Markdown/HTML preview commands.
• Sync bundled and community catalog metadata, README/quickstart references, community extension docs, and default integration command inventories.
• Add a regression test that keeps the bundled preview manifest, catalog entries, release download URL, and default command list aligned.

Compatibility Note

This preserves the breaking command surface from the released preview extension: /speckit.preview.html is removed. Users should migrate to one of the low/mid/high fidelity commands, for example /speckit.preview.mid-html.

Validation

• python extensions\preview\tests\validate-extension.py
• python -m py_compile extensions\preview\tests\validate-extension.py
• python -c "import json; json.load(open('extensions/catalog.json', encoding='utf-8')); json.load(open('extensions/catalog.community.json', encoding='utf-8')); print('catalog json ok')"
• git diff --check
• PYTHONPATH=... python -m pytest tests\test_extensions.py -q (284 passed, 1 skipped)
• PYTHONPATH=... python -m pytest tests\integrations\test_integration_base_yaml.py tests\integrations\test_integration_base_skills.py tests\integrations\test_integration_base_toml.py tests\integrations\test_integration_base_markdown.py tests\integrations\test_integration_cline.py tests\integrations\test_integration_copilot.py tests\integrations\test_integration_generic.py tests\integrations\test_cli.py -q (183 passed, 8 skipped)
• Source CLI smoke test: initialized a temporary project from this branch and confirmed bundled preview installs as v1.1.0 with 6 commands, 6 templates, and 2 schema files.

Notes

A full tests/integrations run was attempted but timed out after 4 minutes locally, so the directly affected integration subsets above were run instead.