docs: refresh FEATURES and COMPARISON against main and the other tools

[debabsah]

The new README (#9) links both pages, so they need to be true first.

FEATURES.md

• Restore rule as it is now: a failure while preparing, importing or updating charts restores the backup automatically, whatever the error; a later failure (linkage, scopes, queries) leaves the new version live.
• New since the last pass: column suggestions, typed MCP errors, microsecond backup names.
• Decompile builds a copy at a new slug, lists most losses, and drops a few settings without a note. Round-trips are lossless for rows and tabs; a sketch comes back as rows.
• Environment promotion needs shared connection names; otherwise one copy per instance.
• SSO and CI-trigger wording aligned with fix: correct the SSO sign-in claim, add --profile to the restore hint, fix CI wording #8. No "adopt", "templating" or sandbox route.

COMPARISON.md

• Facts rechecked 2026-10-03 against the current READMEs of preset-cli (0.3.13), sup (v0.1.6, still beta) and terraform-provider-superset (resources: database, dataset, meta_database, role, role_permissions, user).
• delete-assets now also offers best-effort rollback.
• Adds Superset 6.1.0's built-in MCP service, checked against its source at the 6.1.0 tag.
• plan is no longer described as field by field (it names changed charts and filters); decompile no longer "adopts".

Docs only. Offline suite: 369 passed.