docs: fix build command and ignore compiled binary

Update build command from `go build -o reposcan ./cmd/reposcan` to `go build -o reposcan .` in README.md and CLAUDE.md to reflect that main.go lives at the repo root. Also add `/reposcan` to .gitignore to prevent the compiled binary from being accidentally committed.

Author: frittlechasm

.gitignore

@@ -15,3 +15,4 @@ output-samples/
 # ai stuff
 .claude.local.me
 .serena/
+/reposcan

CLAUDE.md

@@ -11,7 +11,7 @@ RepoScan is a Go CLI tool that scans filesystems for Git repositories and report
 ### Building
 ```bash
 # Build the main binary
-go build -o reposcan ./cmd/reposcan
+go build -o reposcan .
 
 # Install to $GOPATH/bin
 go install github.com/mabd-dev/reposcan@latest

README.md

@@ -43,7 +43,7 @@ Make sure $GOPATH/bin (or $HOME/go/bin) is in your $PATH.
 ```sh
 git clone https://github.com/mabd-dev/reposcan.git
 cd reposcan
-go build -o reposcan ./cmd/reposcan
+go build -o reposcan .
 ```