Add LibSQL and Turso adapter - #13

Merged — thank you. Clean adapter, and the decision to record each batch() statement separately is the right one: a batch loop is exactly where an N+1 hides, and collapsing it into one record would have made this adapter blind to the case it most needs to catch.

I verified it against a real @libsql/client in-memory database rather than only the fake, since that was the part of #1 I could not take on trust:

1 N+1 detected via execute()                   yes, 6× at line 30
2 named args recorded                          [{"id":3}]
3 batch recorded per statement                 6
  N+1 found inside the batch                   yes, 6×
  batch return value preserved                 6 result sets
  params in order                              [[1],[2],[3],[4],[5],[6]]
4 driver error still propagates                LibsqlError
5 restore stops recording                      yes

All correct. One thing that measurement turned up, which I fixed on merge rather than sending back:

per-statement durations (ms)   [0.271, 0.332, 0.382, 0.419, 0.471, 0.511]

Monotonically increasing. The reduce nests each observe() inside the next, so every outer timer contains all the inner ones — the batch took 0.51ms and the six statements reported 2.39ms between them. It scales with batch size: fifty statements would report roughly twenty-five times the truth.

The nesting is genuinely clever and it preserves ordering and the return value correctly, which is why the tests pass. It is only the timing that suffers, and only for batch().

I added observeBatch() in shared.ts: it runs the round trip once and divides the elapsed time evenly across the statements. Drivers give no per-statement timing for a batch, so each statement's duration is an estimate and the sum — which is what a finding actually reports — is the measurement. There is a regression test with a deliberately slow fake asserting the total cannot exceed the real elapsed time.

Also merged main in, since #14 landed in between and changed the Finding shape.

Shipping in 0.6.0 with a changelog credit.