db/snaptype: tolerate files deleted during dir scan

[AskAlexSharov]

ParseDir fails the whole directory scan when a file is deleted between ReadDir and the per-entry DirEntry.Info stat. Merged-over segments are unlinked concurrently with directory scans, so OpenFolder after retire can abort:

[EROR] [snapshots] retire blocks err="open: OpenFolder: lstat .../snapshots/v1.1-047370-047371-transactions.seg: no such file or directory"

Skip entries whose stat returns ErrNotExist (OpenFolder already treats vanished files as retired), and wrap remaining stat errors with the directory for context.

Seen aborting the QA sync-from-scratch (gnosis archive) run on release/3.6: https://github.com/erigontech/erigon/actions/runs/30347797880/job/90237994145

[Copilot]

Pull request overview

This PR hardens snapshot directory scanning in db/snaptype against concurrent file deletion during ReadDir → DirEntry.Info() stat, which can happen when merged-over snapshot segments are unlinked while another goroutine is scanning the directory. It makes ParseDir skip entries that vanish mid-scan instead of failing the whole scan, and adds a targeted unit test for the race.

Changes:

• Refactor ParseDir to delegate entry processing into a helper (parseDirEntries) for testability.
• Skip entries whose DirEntry.Info() fails with fs.ErrNotExist, tolerating concurrent unlink.
• Wrap remaining stat errors with the directory path for better diagnostics, and add a test covering the “vanished entry” case.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
db/snaptype/files.go	Skip ErrNotExist from per-entry stat during scans; wrap other stat errors with directory context; extract parseDirEntries helper.
db/snaptype/files_test.go	Add unit test ensuring a vanished entry during scan is skipped (and does not abort the scan).

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