Function discoverFtsIndexConfig

discoverFtsIndexConfig(
file: string,
expectedVaultRoot: string,
): Promise<FtsIndexDiscovery>
Classify a configured FTS path through the same exact admission logic used by FtsIndex.open, but on one readonly handle and without Enquire bootstrap, persistent PRAGMA mutation, DDL, DML, or chmod. SQLite/VFS lock, recovery, and WAL/SHM bookkeeping remain outside this logical guarantee. The main/WAL/SHM/rollback-journal family is checked before dependency load and again immediately before native open; unsafe, hardlinked, or orphaned leaves collapse to refused under the stable-parent boundary.
Parameters
- file: string
  Configured .fts5.db path.
- expectedVaultRoot: string
  Exact canonical vault root expected to own it.
Returns Promise<FtsIndexDiscovery>
missing or genuinely schema-empty when caller defaults are safe, owned with the physically proven stored tokenizer, or generic refused.
Throws
If file is outside the exact .fts5.db namespace.
Example
```
const discovery = await discoverFtsIndexConfig(indexFile, vaultRoot);
const tokenize = discovery.kind === "owned" ? discovery.meta.tokenize_mode : "unicode61";
const index = new FtsIndex({ file: indexFile, vaultRoot, tokenize });
await index.open(discovery);
```
- Defined in src/fts5.ts:3731