Normalize chains/ directory for Substrate and tar snapshots

[vukomir]

• Add SubstrateChainsDirName (hyphens to underscores) for ChainDBDataPath and RelayChainDBDataPath so on-disk layout matches the node.
• Extend tar extraction to strip chains//db|paritydb/ prefixes using both YAML chain_id and normalized segment; pass chain_id from SyncIfNeeded.
• Add tests for path mapping and snapshot sync with underscore archive paths.

[Copilot]

Pull request overview

Normalizes on-disk chains/ directory naming to match Substrate’s hyphen→underscore behavior, and improves tar snapshot extraction to handle archives that include chains/<id>/<db|paritydb>/... prefixes.

Changes:

• Add config.SubstrateChainsDirName() and use it in ChainDBDataPath / RelayChainDBDataPath.
• Extend tar extraction to rewrite member paths by stripping chains/<id>/<storageDir>/ (matching both YAML chain_id and normalized directory segment).
• Update snapshot sync call sites/signature and add tests for underscore paths in tar archives.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/snapshot/snapshot.go	Adds chain-id-aware tar member path mapping and updates tar extraction to strip chains/<id>/<storageDir> prefixes safely.
internal/snapshot/snapshot_test.go	Adds tests for the new tar path mapping and updates existing SyncIfNeeded call sites for the new signature.
internal/config/config.go	Introduces SubstrateChainsDirName() and applies it to chain DB path construction.
internal/config/config_test.go	Extends fixed-path tests to cover hyphenated chain IDs mapping to underscore directories.
cmd/bootstrap/main.go	Passes YAML chain_id through to snapshot sync for tar path rewriting.

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