Remove unreachable RPC methods

Several RPC server and client methods are unreachable and should be removed:

Server methods (internal/rpc/server.go):
- `Server.GetLastImportTime` (line 2116)
- `Server.SetLastImportTime` (line 2123)
- `Server.findJSONLPath` (line 2255)

Client methods (internal/rpc/client.go):
- `Client.Import` (line 311) - RPC import not used (daemon uses autoimport)

Evidence:
```bash
go run golang.org/x/tools/cmd/deadcode@latest -test ./...
```

Impact: Removes ~80 LOC of unused RPC code

- Remove the 4 unreachable methods (~80 LOC total)
- Verify no callers: `grep -r "GetLastImportTime\|SetLastImportTime\|findJSONLPath" .`
- All tests pass: `go test ./internal/rpc/...`
- Daemon functionality works: test daemon start/stop/operations


Refactor sqlite.go (2298 lines)

Break down internal/storage/sqlite/sqlite.go into smaller, more focused modules. The file is currently 2298 lines and should be split into logical components.


Wrap git operations in GitClient interface

Create internal/daemonrunner/git.go with GitClient interface (HasUpstream, HasChanges, Commit, Push, Pull). Default implementation using os/exec. Use in Syncer and Run loop for testability.


Document bd edit command and verify MCP exclusion

Follow-up from PR #152:
1. Add "bd edit" to AGENTS.md with "Humans only" note
2. Verify MCP server doesn't expose bd edit command
3. Consider adding test for command registration