feat(cli): add interactive config input and Makefile

- support interactive value input for `config set`
- hide API key input and output
- add Makefile for build, test, vet, coverage, and cleanup
- add golang.org/x/term dependency
- update changelog and gitignore

.gitignore

@@ -40,4 +40,9 @@ reasonix.toml
 opencode.json
 .claude/
 .opencode/
-.hermers/
+.hermers/
+
+# Build output (Makefile)
+bin/
+coverage.out
+coverage.html