Document and validate FTS5 idsfind DB requirements for sqlite-wasm backends

[mandel59]

Context

@sqlite.org/sqlite-wasm supports FTS5, but it does not support the FTS4 module used by the existing @mandel59/idsdb idsfind.db.

During mojidata-web-app integration, the sqlite-wasm OPFS backend needed the FTS5 database from @mandel59/idsdb-fts5 instead of the legacy FTS4 @mandel59/idsdb asset.

Problem

The backend requirement is easy to miss. Passing an FTS4 idsfind.db to sqlite-wasm fails only after SQLite tries to open/query the virtual table, which makes the integration error less obvious.

Proposed fix

• Document that sqlite-wasm idsfind requires @mandel59/idsdb-fts5.
• Consider making @mandel59/idsdb-fts5 an explicit dependency or peer dependency of the sqlite-wasm integration package.
• Add schema/version validation for idsfind DBs used by sqlite-wasm.
• Produce a clear error when an FTS4 idsfind DB is supplied to an FTS5-only backend.

Acceptance criteria

• sqlite-wasm docs mention the FTS5 requirement and package name.
• Tests cover successful use with @mandel59/idsdb-fts5.
• Tests cover a clear failure with the FTS4 @mandel59/idsdb DB.

[mandel59]

PR #39 が merge 済みです。

sqlite-wasm backend では idsfind_fts が FTS5 であることを初期化時に検証し、FTS4 DB が渡された場合は @mandel59/idsdb-fts5 を案内する SqliteWasmIdsfindSchemaError を返すようにしました。README にも FTS5 DB 要件と public subpath を追記しています。

完了扱いで close します。