report --db should normalize SQLite file URIs before filesystem checks

[Widthdom]

Problem

cdidx report --db file:... does not follow the same SQLite file-URI normalization path used by query/database readers. It checks the raw string with File.Exists before opening SQLite, so valid file URIs can be reported as missing or shown inconsistently.

Evidence

• ReportCommandRunner.BuildSchemaSummary(string dbPath) calls File.Exists(LongPath.EnsureWindowsPrefix(dbPath)) directly.
• It then builds a SQLite connection from the same unnormalized value.

Suggested fix

Route report DB paths through the shared DB path resolver/URI normalizer, or explicitly reject unsupported URI forms with a structured error.

[Widthdom]

Work started on branch fix-issue3221-3148-3147-3138-3175-3125.