Fix scale titles for index-provided scales

[stagedevices]

Motivation

• Index v2 can list scales directly and some entries were showing the pack title for every scale instead of the individual scale name, so the client must derive per-scale titles from index fields and file paths.
• The index may include a scalaPath or place tenney manifests under tenney/ or tenney/scale-builder.json, which should be used to compute a sensible title when the index title matches the pack title.

Description

• Add scalaPath to CommunityIndexScale and decode scales from index entries so index-provided scales are recognized (CommunityPacksModels.swift).
• Add makeIndexScaleInfos(entry:indexScales:), resolveScaleTitle(...), and a synthesize overload to build pack JSON with per-scale id/title/path for index-driven packs, and wire the index-driven flow into CommunityPacksStore when index.schemaVersion >= 2 (CommunityPacksStore.swift).
• Derive scale IDs with deriveScaleID(from:) and compute resolved fetch paths with resolvedScalePath(...), and use these when fetching and decoding scale payloads so titles reflect scala/tenney path components where appropriate.
• Small supporting changes: treat multiple supported index schema versions via supportedSchemaVersions and use assumedSchemaVersion accordingly, and normalize cached decode labels to use resolved paths.

Testing

• No automated tests or CI were run for these changes.

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Codex Task