refactor(tests): Co-locate tests with source code

Moves all test files from the `tdd/` directory to their corresponding `pkg/` subdirectories. This aligns with standard Go project structure and simplifies the test coverage workflow.

- Moves `tdd/crypt/crypt_test.go` to `pkg/crypt/`
- Moves `tdd/enchantrix/enchantrix_test.go` to `pkg/enchantrix/`
- Moves `tdd/trix/trix_test.go` to `pkg/trix/`
- Simplifies the `Taskfile.yml` to use a standard `go test` command.
- Removes the now-obsolete `tdd/` directory.
- Adds generated coverage files to `.gitignore`.

.gitignore

@@ -2,3 +2,8 @@ node_modules
 package-lock.json
 .idea
 go.sum
+covdata/
+merged_covdata/
+coverage.txt
+coverage.html
+coverage.out

Taskfile.yml

@@ -2,9 +2,9 @@ version: '3'
 
 tasks:
   test:
-    desc: "Run all tests"
+    desc: "Run all tests and generate a coverage report"
     cmds:
-      - go test -v ./...
+      - go test -v -coverprofile=coverage.out ./...
 
   build:
     desc: "Build the project"