Fix SQLite driver name mismatch causing "unknown driver" errors (#252)

* fix: Use correct SQLite driver name 'sqlite3' instead of 'sqlite'

The ncruces/go-sqlite3 driver registers as 'sqlite3', but doctor.go
and example code were using 'sqlite', causing 'unknown driver' errors.

This fix corrects all sql.Open() calls to use the proper driver name:
- cmd/bd/doctor.go: 6 instances fixed
- docs/EXTENDING.md: 2 documentation examples updated
- examples/bd-example-extension-go/: Fixed example code and README

Fixes #230

Amp-Thread-ID: https://ampcode.com/threads/T-1e8c5473-cb79-4457-be07-4517bfdb73f4
Co-authored-by: Amp <amp@ampcode.com>

* Revert CGO_ENABLED back to 0 for pure-Go SQLite driver

The ncruces/go-sqlite3 driver is pure-Go and doesn't require CGO.
The previous change to CGO_ENABLED=1 in commit f9771cd was an
attempted fix for #230, but the real issue was the driver name
mismatch ('sqlite' vs 'sqlite3'), which is now fixed.

Benefits of CGO_ENABLED=0:
- Simpler cross-compilation (no C toolchain required)
- Smaller binaries
- Faster builds
- Matches the intended design of the pure-Go driver

---------

Co-authored-by: Amp <amp@ampcode.com>

.goreleaser.yml

@@ -13,7 +13,7 @@ builds:
     main: ./cmd/bd
     binary: bd
     env:
-      - CGO_ENABLED=1
+      - CGO_ENABLED=0
     goos:
       - linux
       - darwin