FTS initialization and search fallback errors are swallowed without diagnostics

[aeitwoen]

Problem

Search currently has two silent failure paths:

1. FTS initialization errors are swallowed in src/index.ts around sqlite.exec(FTS_SQL)
2. search.search(...) catches any exception and falls back to LIKE in src/core/search.ts

This makes FTS degradation invisible.

Why this matters

Fallback itself is useful for malformed query syntax, but catch-all handling also masks unexpected failures (schema drift, runtime errors, extension issues). Users only see lower quality results and no diagnostics.

Suggested fix

• Surface FTS init failures through logging or an explicit status signal
• Keep fallback for known FTS parse/syntax errors, but do not swallow unrelated exceptions silently
• Expose simple health info so callers can tell whether FTS is active